I wouldn't have gone to college out of state, and then dropped out, for starters. It would completely change where I'm at now, but I'm thinking I would've ended up for the better. I definitely wouldn't have sold my '68 Charger or '68 300, either. Probably wouldn't have bought my house, either, but it's relatively low on the list of things I regret.
Musically, I would've picked up a Les Paul and a Blues Jr. or similar just starting out. I never really jived with my Strat.