I noticed this video the other day from Eric Bloat. Since I don't do youtube videos I figured I'd just post the answer to this question in my blog.
So 6 RPGs that I can't live without.
Basic Fantasy RPG - This game does pretty much everything I need, and could easily be scale-able to any type of game I would like to run.
And since BFRPG does everything I need, I honestly probably wouldn't need any extra games with me. That said I think I would bring a few extra games for flavour.
Original d6 Star Wars, Classic Traveler, Advanced Fighting Fantasy v2.0, mini6 (because you can basically make any game out of it), And a binder with a bunch of retro clones (Lab Lord, Blueholme). I know the last one is a total cop out, but whatever it's my blog.
What would be extremely helpful is a huge book of random tables and one rpg. And If I had room in my duffel bag I'd throw some paper minis in there.
Speaking of desert island, I'm off to warmer climes very soon. So the frequency of posts is going to go down for a bit.
Go on and roll some dice, I'll be back in a week or so.