Which Counter-Strike versions do you own so far? I put 1.3 and 1.5 up there since they are two of the old really well played and liked versions, well mostly on LAN but still out there.
I own 1.6, CZ, and Source. I play 1.6 the most and Source because of friends that have it and they play. I never played CZ lol.
You can pick as many as you want but be truthful.