Constitutional Amendment: Congress may pass no law to which they are immune or to which they alone benefit.

Prohibit Congress from legislating laws that apply to citizens of the United States with embedded clauses that exclude members of Congress from being subjected equally to that law; laws that provide members immunity from current or previously passed legislation, or laws to which members alone stand to benefit to the exclusion of those outside the legislative body, from appropriations to insider trading.
Imagine if our country had a legislative body more concerned with the welfare of the nation and real problem-solving, rather than personal wealth building, self-entitlement, and legislating the favor of campaign donors. Issues like the looming insolvency of Social Security would likely get immediate attention if all our problems were amended to be their problem as well.