The most popular legal questions by far are about marijuana - what states is it legal to buy grow, possess, etc. The second most popular legal questions seems to be about firearms - specific states and the rights to buy, carry, shoot, kill, etc. Third are the questions about sex - minors, age of consent, can a _ year old be with a _ year old, etc.
After that it starts to settle down but the best legal searches are the very, very specific ones (as you'll be seeing), but also the ones that are very obviously legal or illegal and you'll be seeing those posted, too. In some of them, you can almost hear the searcher's voice - they're pissed off about something that's happened to them and they're rushing to to the Internet to check on its legality. Those are some of my favorites, and I'll definitely be posting them.