XCOM is $17.50 on GMG today. It's 50% off and stacks with the 30% off coupon (GMG30-DPLIM-DN831).
I'm still on the fence about it though. I still hear it's quite buggy and there haven't been any patches for it. I watched some let's play videos on YouTube back after its release, and it looks repetitive and might get bored with it after a while.