All the major rights should be granted at the same age- voting, drinking, serving, etc. I say this age should be 18.

Driving should be 100% granted at 18 with trial periods (ie: Drive only to school and work, drive only with a parent, drive with a higher insurance fee, can only drive normal vehicles (ie: no motorcycles, semis, etc)), and the "lighter" drugs (tobacco, marijuana) should be legal sooner.

Most rights should be granted at birth- freedom of speech being an obvious example.