I used to host bi-yearly lan parties. Here are some of the titles we used:
Armagetron Advanced - TRON type racing game
Garrison Gang 2 - Like Team Fortress 2, but 2D, pixelated, side scrolling, more cartoony. It's windows only, but plays fine in wine/crossover
Madballs in Babo:Invasion - Steam game, you play one of those goofy balls from the 80's. Supports coop and versus modes
DOTA 2 (Steam) - DOTA 1 (warcraft 3 mod) had a mode with AI bots, and it was fun to play against them as a team. Haven't played DOTA 2 much, but I think it supports something similar. Note that DOTA is fun as long as everyone is at the same skill level. If your skill levels differentiate too much, it can be frustrating. You can also look at several other MOBA style games, like
Galcon Fusion - Simple clicky strategy game where you try to take over all the planets. Plays fast.
Left4Dead2 - already mentioned
The games above were selected because I had a mixed windows/mac group to support, with old and new hardware. Also not everyone was a serious gamer. So I picked games that typically had low requirements, and played fast, where player elimination was rare or the games were short
Other games you could consider:
Warcraft 3/Starcraft 2 - From Blizard, RTS games
Civilization 5 or 6 - My wife and I play this together on a team against the AI, or you can play against each other.
Borderlands 2, if you get it on steam it supports multiplayer. Steam should be having a big sale to pick up this, portal, civ, etc cheaply, in a few weeks
Trine 1/2/3 - also on steam. Mostly nonviolent platform/puzzler
AI Wars - Steam, brutally difficult. Read the strategy guides
Total War franchise - Steam. I liked Total War: Shogun 2 a lot. Do some research to find a flavor that interests you
Terraria - like a cross between minecraft and zelda - multiple platforms
HOARD - steam. You're a dragon, stealing treasure from humans... and other dragons
Serious Sam HD - steam. It's an FPS, but its coop, you versus hordes and hordes and hordes of mobs.
Payday/Payday 2 - steam - FPS, you work together to rob banks against the AI police
Keep Talking on Nobody Explodes - fun party game where you have t diffuse a bomb, only the person diffusing the bomb doesn't have the instructions and the person with the instructions can't see the bomb. Communication is where things go wrong