Well, I have a few regrets myself.
Like other guys, I wish I would have tried harder. I wasn't a bad student, but I could have worked harder.
I never asked out the girl I liked
I pretty much missed most of my Senior sports because of injuries (nothing I could really do about it, but still)
Also, I skipped 8th grade (went straight to freshman year from 7th). Sometimes I Wish I wouldn't of done it, it really messed with my social life.