GUARANTEE AGREEMENT Between GAINSCO, INC. as Guarantor, and U.S. BANK NATIONAL ASSOCIATION as Guarantee Trustee, Dated as of December 21, 2006

Exhibit 4.16

GUARANTEE AGREEMENT

Between

GAINSCO, INC.

as Guarantor,

and

U.S. BANK NATIONAL ASSOCIATION

as Guarantee Trustee,

Dated as of December 21, 2006

GAINSCO CAPITAL TRUST I

Certain Sections of this Guarantee Agreement relating to

Sections 310 through 318 of the

Trust Indenture Act of 1939:

Note: This reconciliation and tie shall not, for any purpose, be deemed to be a part of the Guarantee Agreement.

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TABLE OF CONTENTS

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GUARANTEE AGREEMENT

THIS GUARANTEE AGREEMENT, dated as of December 21, 2006, is executed and delivered by GAINSCO, INC., a Texas corporation (the “ Guarantor ”), having its principal office at 3333 Lee Parkway, Suite 1200, Dallas, Texas 75219, and U.S. BANK NATIONAL ASSOCIATION, a national banking association, as trustee (“ U.S. Bank National Association ”), for the benefit of the Holders (as defined herein) from time to time of the Capital Securities (as defined herein) of GAINSCO STATUTORY TRUST II, a Connecticut statutory trust (the “ Issuer Trust ”).

Pursuant to an Amended and Restated Trust Agreement (the “ Trust Agreement ”), dated of even date herewith, among Gainsco, Inc., as Depositor, and U.S. Bank National Association, as Property Trustee, the Administrators named therein and the Holders from time to time of undivided beneficial interests in the assets of the Issuer Trust, the Issuer Trust is issuing up to $18,000,000 aggregate Liquidation Amount (as defined herein) of its Floating Rate Capital Securities, representing preferred undivided beneficial interests in the assets of the Issuer Trust and having the terms set forth in the Trust Agreement (the “ Capital Securities ”);

The Capital Securities will be issued by the Issuer Trust and the proceeds thereof, together with the proceeds from the issuance of the Issuer Trust’s Common Securities (the “ Common Securities ”), representing common undivided beneficial interests in the assets of the Issuer Trust, will be used to purchase the Junior Subordinated Debentures of the Guarantor due March 15, 2037 (the “ Junior Subordinated Debentures ”), which will be deposited with U.S. Bank National Association, as Property Trustee under the Trust Agreement, as trust assets; and

As an inducement to the Holders to purchase the Capital Securities, the Guarantor is willing to irrevocably and unconditionally agree, to the extent set forth herein, to pay to the Holders of the Capital Securities the Guarantee Payments (as defined herein) and to make certain other payments on the terms and conditions set forth herein.

NOW, THEREFORE, in consideration of the purchase of the Capital Securities by each Holder, which purchase the Guarantor hereby acknowledges shall benefit the Guarantor, the Guarantor, intending to be legally bound hereby, executes and delivers this Guarantee Agreement for the benefit of the Holders from time to time of the Capital Securities.

ARTICLE I. DEFINITIONS

SECTION 1.1. Definitions.

As used in this Guarantee Agreement, the terms set forth below shall have the following meanings. Capitalized terms used but not otherwise defined herein shall have the meanings assigned to such terms in the Trust Agreement.

“Affiliate” of any specified Person means any other Person directly or indirectly controlling or controlled by or under direct or indirect common control with such specified Person. For the purposes of this definition, “control” when used with respect to any specified Person means

the power to direct the management and policies of such Person, directly or indirectly, whether through the ownership of voting securities, by contract or otherwise; and the terms “controlling” and “controlled” have meanings correlative to the foregoing.

“ Debenture Redemption Date ” means, with respect to any Junior Subordinated Debenture to be redeemed, the date fixed for such redemption by or pursuant to the Indenture.

“Event of Default” means (i) a default by the Guarantor in any of its payment obligations under this Guarantee Agreement, or (ii) a default by the Guarantor in any other obligation hereunder that remains unremedied for 30 days after receipt by Guarantor of written notice of such default.

“Guarantee Agreement” means this Guarantee Agreement, as modified, amended or supplemented from time to time.

“Guarantee Payments” means the following payments or distributions, without duplication, with respect to the Capital Securities, to the extent not paid or made by or on behalf of the Issuer Trust: (i) any accumulated and unpaid Distributions (as defined in the Trust Agreement) required to be paid on the Capital Securities, to the extent the Issuer Trust shall have funds on hand available therefor at such time, (ii) the Redemption Price, with respect to the Capital Securities called for redemption by the Issuer Trust, to the extent that the Issuer Trust shall have funds on hand available therefor at such time, and (iii) upon a voluntary or involuntary dissolution, termination, winding-up or liquidation of the Issuer Trust, unless the Junior Subordinated Debentures are distributed to the Holders, the lesser of (a) the aggregate of the Liquidation Amount of all outstanding Trust Securities and all accumulated and unpaid Distributions to the date of payment, to the extent the Issuer Trust shall have funds on hand available to make such payment at such time and (b) the amount of assets of the Issuer Trust remaining available for distribution to Holders on liquidation of the Issuer Trust (in either case, the “ Liquidation Distribution” ).

“Guarantee Trustee” means U.S. Bank National Association, until a Successor Guarantee Trustee has been appointed and has accepted such appointment pursuant to the terms of this Guarantee Agreement and thereafter means each such Successor Guarantee Trustee.

“Guarantor” shall have the meaning specified in the first paragraph of this Guarantee Agreement.

“Holder” means any holder, as registered on the books and records of the Issuer Trust, of any Capital Securities; provided, however, that, in determining whether the holders of the requisite percentage of Capital Securities have given any request, notice, consent or waiver hereunder, “Holder” shall not include the Guarantor, the Guarantee Trustee, or any Affiliate of the Guarantor or the Guarantee Trustee.

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“Indenture” means the Junior Subordinated Indenture, dated of even date herewith, between the Guarantor and U.S. Bank National Association, as trustee, as it may be modified, amended or supplemented from time to time.

“Issuer Trust” shall have the meaning specified in the first paragraph of this Guarantee Agreement.

“Like Amount” means (a) with respect to a redemption of Trust Securities, Trust Securities having a Liquidation Amount equal to that portion of the principal amount of Junior Subordinated Debentures to be contemporaneously redeemed in accordance with the Indenture, allocated to the Common Securities and to the Capital Securities based upon the relative Liquidation Amounts of such classes and (b) with respect to a distribution of Junior Subordinated Debentures to Holders of Trust Securities in connection with a dissolution or liquidation of the Issuer Trust, Junior Subordinated Debentures having a principal amount equal to the Liquidation Amount of the Trust Securities of the Holder to whom such Junior Subordinated Debentures are distributed.

“Liquidation Amount” means the stated amount of $1,000 per Capital Security and $1,000 per Common Security.

“Majority in Liquidation Amount of the Capital Securities” means, except as provided by the Trust Indenture Act, Capital Securities representing more than 50% of the aggregate Liquidation Amount of all then-outstanding Capital Securities.

“Officers’ Certificate” means a certificate signed by the Chairman of the Board, Vice Chairman of the Board, Chief Executive Officer, President, Executive Vice President or a Senior Vice President or Vice President, and by the Treasurer, an Assistant Treasurer, the Chief Financial Officer, the Secretary or an Assistant Secretary of the Guarantor, and delivered to the Guarantee Trustee. Any Officers’ Certificate delivered with respect to compliance with a condition or covenant provided for in this Guarantee Agreement shall include:

(a) a statement by each officer signing the Officers’ Certificate that such officer has read the covenant or condition and the definitions relating thereto;

(b) a brief statement of the nature and scope of the examination or investigation undertaken by such officer in rendering the Officers’ Certificate;

(c) a statement that such officer has made such examination or investigation as, in such officer’s opinion, is necessary to enable such officer to express an informed opinion as to whether or not such covenant or condition has been complied with; and

(d) a statement as to whether, in the opinion of such officer, such condition or covenant has been complied with.

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“Person” means a legal person, including any individual, corporation, estate, partnership, joint venture, association, joint stock company, limited liability company, trust, unincorporated association, or government or any agency or political subdivision thereof, or any other entity of whatever nature.

“Redemption Date” means, with respect to any Capital Security to be redeemed, the date fixed for such redemption by or pursuant to the Trust Agreement; provided that each Debenture Redemption Date and the stated maturity date of the Junior Subordinated Debentures shall be a Redemption Date for a Like Amount of Capital Securities, including, but not limited to any date of redemption pursuant to the occurrence of any Special Event.

“Redemption Price” shall have the meaning specified in the Trust Agreement.

“Responsible Officer” means, when used with respect to the Guarantee Trustee, any officer assigned to the Corporate Trust Office of the Guarantee Trustee, including any managing director, vice president, principal, assistant vice president, assistant treasurer, assistant secretary or any other officer of the Guarantee Trustee customarily performing functions similar to those performed by any of the above designated officers and having direct responsibility for the administration of this Guarantee Agreement, and also, with respect to a particular matter, any other officer of the Guarantee Trustee to whom such matter is referred because of such officer’s knowledge of and familiarity with the particular subject.

“Senior Indebtedness” shall have the meaning specified in the Indenture.

“ Special Event ” shall have the meaning specified in the Indenture.

“Successor Guarantee Trustee” means a successor Guarantee Trustee possessing the qualifications to act as Guarantee Trustee under Article IV hereof.

“Trust Agreement” has the meaning specified in the recitals hereto.

“Trust Indenture Act” means the Trust Indenture Act of 1939 (15 U.S.C. §§ 77aaa-77bbbb) and any successor statute, in each case as amended.

“Trust Securities” means the Common Securities and the Capital Securities.

ARTICLE II. TRUST INDENTURE ACT

SECTION 2.1. Trust Indenture Act; Application.

If and to the extent any provision hereof limits, qualifies or conflicts with a provision of the Trust Indenture Act that is required under such Act to be a part of and govern this Guarantee Agreement, the provision of the Trust Indenture Act shall control. If any provision of this Guarantee Agreement modifies or excludes any provision of the Trust Indenture Act that may be so modified or excluded, the latter provision shall be deemed to apply to this Guarantee Agreement as so modified or excluded, as the case may be.

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SECTION 2.2. List of Holders.

(a) The Guarantor will furnish or cause to be furnished to the Guarantee Trustee a list of Holders at the following times:

(i) quarterly, not more than 15 days after the last day of February, May, August and November, in each year, a list, in such form as the Guarantee Trustee may reasonably require, of the names and addresses of the Holders as of the last day of February, May, August and November, as applicable; and

(ii) at such other times as the Guarantee Trustee may request in writing, within 30 days after the receipt by the Guarantor of any such request, a list of similar form and content as of a date not more than 15 days prior to the time such list is furnished.

(b) Notwithstanding Section 2.2(a), no such list need be furnished, if and so long as the Guarantee Trustee is the Securities Registrar (as defined in the Trust Agreement).

(c) The Guarantee Trustee shall comply with the requirements of Section 311(a), 311(b) and 312(b) of the Trust Indenture Act.

SECTION 2.3. Reports by the Guarantee Trustee.

Not later than January 31 of each year, commencing January 31, 2007, the Guarantee Trustee shall provide to the Holders such reports, if any, as are required by Section 313 of the Trust Indenture Act in the form and in the manner provided by Section 313 of the Trust Indenture Act. If this Guarantee Agreement shall have been qualified under the Trust Indenture Act, the Guarantee Trustee shall also comply with the requirements of Section 313(d) of the Trust Indenture Act.

SECTION 2.4. Periodic Reports to the Guarantee Trustee.

The Guarantor shall provide to the Guarantee Trustee and the Holders such documents, reports and information, if any, as required by Section 314 of the Trust Indenture Act and the compliance certificate required by Section 314 of the Trust Indenture Act, in the form, in the manner and at the times required by Section 314 of the Trust Indenture Act, provided that such documents, reports and information shall be required to be provided to the Securities and Exchange Commission only if this Guarantee Agreement shall have been qualified under the Trust Indenture Act.

SECTION 2.5. Evidence of Compliance with Conditions Precedent.

The Guarantor shall provide to the Guarantee Trustee such evidence of compliance with such conditions precedent, if any, provided for in this Guarantee Agreement that relate to any of the

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matters set forth in Section 314(c) of the Trust Indenture Act. Any certificate or opinion required to be given by an officer pursuant to Section 314(c)(1) may be given in the form of an Officers’ Certificate.

SECTION 2.6. Events of Default; Waiver.

The Holders of a Majority in Liquidation Amount of the Capital Securities may, by vote, on behalf of the Holders, waive any past Event of Default and its consequences. Upon such waiver, any such Event of Default shall cease to exist, and any Event of Default arising therefrom shall be deemed to have been cured, for every purpose of this Guarantee Agreement, but no such waiver shall extend to any subsequent or other default or Event of Default or impair any right consequent therefrom.

SECTION 2.7. Event of Default; Notice.

(a) The Guarantee Trustee shall, within 90 days after the occurrence of an Event of Default, transmit by mail, first class postage prepaid, to the Holders, notice of all Events of Default known to the Guarantee Trustee, unless such Events of Default have been cured or waived before the giving of such notice; provided that , except in the case of a default in the payment of a Guarantee Payment, the Guarantee Trustee shall be protected in withholding such notice if and so long as the Board of Directors, the executive committee or a trust committee of directors and/or Responsible Officers of the Guarantee Trustee in good faith determines that the withholding of such notice is in the interests of the Holders.

(b) The Guarantee Trustee shall not be deemed to have knowledge of any Event of Default unless the Guarantee Trustee or a Responsible Officer charged with the administration of this Guarantee Agreement shall have received written notice of such Event of Default.

SECTION 2.8. Conflicting Interests.

The Trust Agreement shall be deemed to be specifically described in this Guarantee Agreement for the purposes of clause (i) of the first proviso contained in Section 310(b) of the Trust Indenture Act.

ARTICLE III. POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE

SECTION 3.1. Powers and Duties of the Guarantee Trustee.

(a) This Guarantee Agreement shall be held by the Guarantee