Earlier today, Capcom held an event in downtown Toyko to specifically to show off Dead Rising 2 - the game didn't make a big appearance at TGS, presumably because of how graphic it is. It was at this event that Keiji Inafune let the cat out of the bag on Dead Rising 2's multiplayer. As revealed in the TGS trailer, Dead Rising 2 centers around a game show called "Terror is Reality" that challenges contestants to a series of odd, almost Takeshi's Castle-like events. Terror is Reality is seems to be mainly a driving force behind the multiplayer, though it does play some role in the single player as well.
The event showcased four of the multiplayer events, though the total amount of events is still being decided upon. At the event, the multiplayer was 4 player online only, though Capcom wouldn't rule split screen out of the picture yet. Also of note is that Capcom explicitly said that the multiplayer had only been announced for the XBox 360 version, but I doubt PS3 fans have much to worry about in that regard.
The multiplayer games shown at the Dead Rising 2 event were called Ramster Ball, Pounds of Flesh, Slicycles, and Headache, deatailed as followed.