Looking for a online/lan game

I'm looking for an online/lan multiplayer game me and a few buddies can play together on our off days.  
Does anyone have any suggestions as to what we should try? None of us can think of anything.  We used to play Age of Empires (Various versions) and Counter Strike together, but we grew tired of them after so long.  
No game types are off limits, suggest any game! Except for games with monthly/yearly fees. 
Don't recommend Left 4 Dead or Call of Duty series, played to death already. 
We would prefer it just be us playing together, so dedicated servers and password locked rooms are a plus. (Glares at Modern Warfare 2)

Alien Swarm is free. And next week Starcraft 2 comes out.

Give alien swarm a try. It's great fun to play with with friends. You can play it on LAN with some tricks.