For those with HL2:DM, I've got great co-op and puzzle building maps! If you've got HL2 only, try garry's mod 9 (a free 30MB addon) which offers great mini-games, sandbox and co-op. I'd like to play sourceforts as well, a build your own fortress with steel plates and CTF battle game. Fun for 2 even! If you've got other great co-op mods to share, tell me!

I'll be creating servers if you'd play!

Just messing around with Steam, have a pleasant day.