Runequest, because Glorantha is awesome and it's an endless source of stories, even if i'm not so fan of the BRPG.
A generic pulpy system, maybe Savage Worlds, maybe another one, something that can be tweaked according to my needs and whims.
The One Ring, because Middle Earth is one of my first loves and it's the game that catches the best the mood of this world.
And tons of paper and pencils because designing systems is a big part of the fun.