As of yesterday, you can download a 2D clone version of Counter Strike from Gamershell.com. The clone is made by Unreal Software, it was completely programmed in Blitz 3D and although in 2D, it's still a fun game.
The game features Online Gaming (www and LAN), but you can also play it offline using Bots. The game still has Hostage Rescue and Bomb Planting missions and it kept a lot of original weapons while introducing a couple of new ones.
The game is also listed to have 3D accelerated Special FX and 3D sounds, but don't expect wonders. We'd say that it's a good workplace alternative to Counter Strike, especially knowing that you can play it online. (Uhm, so now you're playing Counter at the workplace? Where did I leave those pink slips... sub.ed.)
You can download the game here.