Some free 2 play options for the PC:
Champions Online
DC Universe Online
F.E.A.R. Online
Star Trek Online
Star Wars: The Old Republic
PS3 games with online multiplayer:
Batman: Arkham Origins
Diablo III
The Last of Us
Tomb Raider
WWE 2K14
Xbox 360 options to throw in the ring:
Destiny
Halo series
GTA V (oh god yes!)
Minecraft (yay!)
Burnout Paradise (this can be hilarious with a group of people as we have proven in the past)
Red Dead Redemption (Throwing Knife Joust anyone? Horse racing? Boar Punching?)
When are you planning on hitting this up? Matt and I have a single copy. xD
I could do Age of Empires II
Age of the Empires goes up to something like 8 players, so we could feasibly get a bunch of us in for AoE.