The best thing to come out of Gears of War 2 was Horde mode. Since then, a plethora of games have adopted similar modes of co-op play. Now, Epic is taking the next step (and a page from Valve’s Left 4 Dead 2 book), and introducing Beast mode.
Beast mode takes Horde mode and spins it around. You spawn as one of the Locust Horde and your mission is to take down the COGs. As in Left 4 Dead 2, you can spawn as any different enemy type, but in Gears 3 killing earns you tokens which can then be spent on respawning as different Locust characters.
Cliffy B has confirmed that Horde mode isn’t going anywhere. Along with 4 player co-op through the entire campaign and the standard multiplayer mode, Gears of War 3 is going to be full of ways to kill and be killed. April 2011 can’t come soon enough.