Steam is offering (the new) DOOM for 50% off this week. That's the best discount I've seen so far on a game that seems to have come out much better than anyone predicted. I've not played it myself, yet, but do plan to get it for the single-player campaign.
It's excellent. I would still be in its throes if my save hadn't gotten corrupted, forcing me to restart.
If you try to take cover, you've already lost.