Very hard to organize with all overstated DRM, but definately a solid game to play with mates (probably my favorite RTS game and I've never touched the single player).meowchef said:Company of Heroes
I'd also play DotA (never took to WC3 multiplayer outside of it, always liked it more than demigod), Killing floor, Alien vs Predator 2 (new one coming out soonish I beleive), Hidden: Source, Dystopia (probably the best mutliplayer game I've touched), UT2004 (3 didn't do much for me, also annoying to lan), diablo (both are good, but not too often), civ 4 (if you have unlimited time), starcraft and dawn of war (+expansions, the second one had severe map shortages and probably isn't worth the effort).