Hmm... Morrowind. Unlimited potential for growth, with alchemy and enchantments.
I'd spend years learning the correct skills, then, one fateful day...
I'd put on my full suit of restore health (constant), drink all of my stockpiled +endurance/strength/acrobatics potions, and LEAP INTO SPACE.
I'd be constantly healing, so pressure/oxygen shouldn't be a problem- given how health works in Morrowind, that is.
EDIT: Oh, fuck it- What am I thinking? Pokemon. As long as I have some way of getting a starter that doesn't involve stealing pokeballs until I'm lucky enough to catch one... How *are* non-official trainers supposed to do that, anyway?