Avenging Spirits. When I was younger, a friend and I loaned each other a bunch of our games. Sadly, he ended up moving away before we managed to swap back, and he got the better end of the deal when it came to the games. However, I did get left with a copy of Avenging Spirits… the game is a bit strange but its very fun and the sprite work is just adorable.
The game has you playing as a spirit who can possess enemies. You start off with a few you can possess, and then you gain more choices as you progress. Or so I believe… I wasn’t all that good at the game back in the day, so I don’t remember getting too far in it.
I suppose it depends on how much I can bend the rules…
If I’m allowed to use the console only ‘as-is’, then probably the Nintendo DS. This gives me DS games (which are great), but also GBA games as well (though you’ll miss out on GBC/GB games, which is a bit sad); this also nets you a smattering of NES/SNES ports to boot, so that’s nice. But most importantly, it gets me Chrono Trigger and a bunch of my favorite Castlevania games all in one place (sad that SotN doesn’t get here, but…)
If I’m allowed to use the console with no hold’s barred, then Playstation Vita. Mod that little sucker and you’ve got access to a ton of stuff… PSV games obviously, but emulated PS1, PSP, GBA, GBC, GB, NES, SNES, and Genesis also (and maybe more, I don’t think I’ve tried any others though).