Gears of War/Multiplayer modes

Warzone
Warzone is your standard kill the whole other team deathmatch setting.

Assassination
In assassination one player on each team is chosen as the leader. In order for the round to be completed the leader of one team must be killed. Once the leader is dead the round will end, regardless of how many other players are left.

Execution
In execution for a player to die they must be executed. When you shoot them normally they will only go down they will not die, and they will get up by themselves if they are not executed or revived by a teammate. An execution qualifies as a headshot from a sniper rifle, a chainsaw kill, a curbstomp, a close up shotgun blast, a meleed grenade, or a powered up torgue bow shot.