Online Game: Endless Zombie Rampage 2
"The endless rampage continues! Re-kill zombies, do missions, and upgrade weapons! You can map your keys in the pause menu, as well as turn on/off various visual effects. Did not even know a sequel was being worked on. Capitalizes on the same game play as the original but this time with much more varied levels."
This game is very badass. It's hard to compete with my last entry, GunGirl 2, but that wasn't even technically an online game. There's so many zombies to be eradicated in Rampage 2, and plenty of ways to kill them. Click on the picture above to try the areal-view, Diseased Productions-made game out at ZombieGames.