Steve the miner, a la Minecraft.
Frankly, I'm thinking this is a pretty good matchup. I'll admit, I would rather have some badass like Isaac Clarke or Master Chief at my back, but Steve can not only make a shelter, he can create anything he wants to. Is the apocalypse a zombie invasion? Steve's dealt with the undead. All we'd need is some cobblestone and we'd be set; insta-fortress. Inside the fortress we can get a farm going, plant some trees, and live out our lives in peace. We'd start our own mining system, get diamonds, and then kick ass. If the apocalypse were some sort of world-destruction sort of thing, well, we'd just built ahead of it. Also, minecraft blocks float. Worst case scenario we build a new world. Alien invasion? Um... Well, that would prove interesting, but we could always portal to the Nether and survive there. Not that that's much better... I'm sure we could devise some sort of offense using TNT though.
All in all, not the best partner, but not a bad one either.