Mount and Blade Warband is 75% off on steam right now. http://store.steampowered.com/app/48700/ It has a FPS/Hack and slash team deathmatch and deathmatch multiplayer, and the single player is a lot of fun too.
I wish multiplayer was better but single player is good. Though after a while its just the exact same thing over and over and over. Once you get a good army you can dominate anyone with easy. Can even take out entire armies solo if you are on a warhorse.
There is a large modding community as well that puts out some great stuff for the game. http://www.mbrepository.com/
Anyone ever play the old game called Rune? Reminds me of this. Except I think it was third person hack and slash multiplayer. Was awesome either way.