Yeah, okay, I can't narrow it down to one either.
Samus Aran: Hell, if anything, being gender-swapped would be an interesting experience, though a reversion clause would certainly be nice. Regardless, though, it'd all be worth it for her power suit. Space jump, speed booster and of course the morph ball. How could that not be fun?
Crono: Time-traveling hero with the best group of friends imaginable. Also, in the process of marrying his true love (and battle buddy/action girl), he ends up on the throne of his homeland. I could bring REFORM and DEMOCRACY to that primitive land! ...Or, according to Chrono Cross, get murdered off-screen during the invasion of my kingdom by a nation I accidentally empowered in the distant past. I'd, uh, have to do something about that, yes...
Commander Shepard: Adventure, heroism, romance...IN SPACE