Definitely travel. It would've been nice to be able to get out of the states for a few weeks before I had all of the responsibilities that come with a full-time job, folks depending on me, a whole-ass flock of birds, etc etc.
My goal is now to (hopefully) travel before I'm 40 (currently 34, 35 in October). I'd like to hit up the UK (I've got a good friend there) and Japan (I'm a huge weeb), if possible.
My advice to the youngins out there: If you've got the means, definitely do a bit of travel between either highschool and college or college and a full-time job.
It's more fun, and mostly harmless, to believe these kinds of little stories happened. Life's more interesting that way.