Preordering Sucker Punch's inFamous will get you more than just one good game, it'll get you into a multiplayer beta of another blockbuster game, Naughty Dog's Uncharted 2: Among Thieves. Completely unknown is what the multiplayer entails. Co-op would be nice, though it wouldn't be suitable for a beta. Deathmatch would be cool too, as would capture the flag and a headquarters style game. More details should emerge on Monday when SCE makes their "electrifying announcement".
The multiplayer beta code is for sure available at Best Buy, and will most likely be available at GameStop and other purchase outlets.