This game is insanely fun.(A little hard,since it's multi player-only).
It's best described as a first-person slasher.
Take your usual first-person shooter,replace the guns with swords,maces,and spears..and set it during medieval times.
Beautiful graphics,and IMO it's very addictive.
(I've played 52 minutes so far last night,and considering I have to go to work this morning starting at 8 AM..I'm tempted to start playing but worried I'll be late for work if I do start playing.)
http://store.steampowered.com/app/219640/
It's 50% off on Steam this weekend,ending Jan.28,2013.