Get The Witcher games.
If you like twin stick games Beat Hazard Ultra and Waves are really good. Beat Hazard Ultra uses your own music collection to power your weaponry with the with nuances of the music influencing the intensity of your ships main gun which manifests as a sort of difuse pulsating cloud of energy. Fire an album on and play Survival, it's fun.
You've still got time to pick up Orcs Must Die in the Steam sale for 2 quid, well worth getting. It's a twist on the Tower Defence genre with you playing the part of a Rift Guardian who has to protect these Rift portal thingys from waves or Orc attacks. Rather than towers you place traps along the Orcs path towards the Rift Portals, at the same time you fight the Orcs in 3rd person view with a variety of magic weapons. The story and humour don't really do it for me but the gameplay is good enough to look past that.
Speaking of Tower Defence, Defence Grid: The Awakening is still a good game and will no doubt appear on sale at some point during the Steam Sale.
Also, it's often worth getting any multi-plat titles you fancied but never got around to getting on console (if the PC version is well done anyway) because you'll find you can pick many of them up for under a fiver on Steam in the sales and you get to play them at higher resolution with better lighting and effects to boot.
If you get BF3 add me up, freedoms_stain on Origin and Battlelog, I already sent you a Steam invite.
