If you like Left 4 Dead, you'd probably like Vermintide. It's basicslly the same thing. A little more varied in missions, tho, since you do more than just run to a safe room.

Pretty much what Kolanaki said. It's just you and some teammates carving your way through ratmen and undead hordes, but it is fun for that kind of "just want to get in and play some rounds" without having to deal with a ton of story or plot. Especially if you're looking for something medieval/fantasy themed.