Game just went into beta, so I think it's worth a mention (that and because it's an awesome game)
Door Kickers - $11.99 (20% off)
So you might be thinking "Why do I need this game if I already have Frozen Synapse?". Now Door Kickers was one of the first PC games I bought, and while Frozen Synapse may be king in terms of multiplayer, I feel like Door Kickers is superior in other aspects. I enjoy the realistic SWAT setting and aesthetic far more than FS's sci-fi style. Frozen Synapse focuses on warfare; Door Kickers focuses on controlled planning and precise team work and meticulous assaults. Go in loud or stealthy, rescue hostages, arrest bad guys, defuse bombs. There's a ton of content, modding, a level editor, a leveling-up system for your squad, and special challenges for each mission