As people have mentioned stalker (the first is probably the best, especially with the Oblivion Lost mod), orange box, Wasn't a massive fan of Supcom tbh. for a crushingly deep Strategy game, Civ4 is excellent (and the complete edition is only a couple of £ now) Arkham Asylum is also worth a play (if you haven't on consoles) Shattered horizon is also a pretty fun Zero g FPS (send me a PM and i can give you a 3 day guest pass) and should certainly test out your rig, although it is DX10 only, so you will need vista or 7.
Arma 2 Crysis Warhead & Crysis Battlefield 2 - old but still great fun Flight Sim X S.T.A.L.K.E.R. Shadow of Chernobyl (with Complete mod 2009) Borderlands Half Life 2 & Episodes 1 & 2 Portal Call of Juarez 1 (not Bound in Blood (lazy console port)) - much DX10 goodness and yes, Far Cry is still excellent.
Thanks again guys! I'm loving TF2 at the moment and looking forward to playing HL2 and L4D2 plus countless other games!
