Quake live is quite fun played with buddies but could be frustrating cause lots of veterans playing it and the most of the time you are dead without even noticing it.
Can't really recommend the new H1Z1 - King of the Kill but if you have some friends to play with and you like to gimp you char with swag clothes and stuff it's worth a try.
Tribes Ascend , f2p , pewpew , not very popular atm.
Dirty Bomb , f2p , pewpew , might get boring.
TF2 with the new matchmaking system (in beta i think) , pewpewpewpewpew , hats.
Gunz: the Duel , never tried it but heard it was fun and challenging.
Brawlalla , platform , melee.
Duelyst , TCG , no pewpew , ranking.
Most of the top games are already mentioned so i stop here.