What are some laws that discriminate against age or gender or sexuality in the US?

In the United States, the vast majority of laws are nondiscriminatory. Some however, do come to mind. Here is a sampling of such laws:

A. In Washington DC, voters cannot vote for candidates for president. This holds true for the Commonwealth of Puerto Rico and all other US Territories such as the American Virgin Islands;

B. Some US States do not allow same sex marriages, however, based on recent Supreme Court rulings on related issues concerning same sex marriage, it seems at some point all States will allow this;

C. The drinking of alcoholic beverages is based on age in the US States. It is unlikely that these laws will change to any large extent;

D. There are age restrictions on the minimum age for the office of president and congressman - women.

E. There are age requirements for public office holders among the US States public offices; and

F. There are age requirements for joining the US Armed forces.