There is one simple browser game of the survival dystopian genre which attracts some S.T.A.L.K.E.R and Resident Evil fans. It's advertised as an MMO game but only 4-6 players can join a multiplayer session simultaneously. The game is called Dead Frontier. A 3D version of the game is supposed to be released later this year.
The game is simple. You create a character, choose a profession and start going into the city from a protected outpost to search for food, ammunition, medical supplies, armor and weapons. The further you go into the city, the harder zombies you will encounter and the better loot you may find. Eventually, you always return back to the outpost where you can trade your items with a few thousand other players. Your character gains experience points and levels for killing monsters and each level you can assign some skill points to weapon skills and to general skills. Your character becomes better and gains the ability to use better weapons. The main thrill in the game is to try to get to the deepest part of the city, survive there as long as you can and find a really good and very rare weapon or armor. There is also a low chance of encountering a special zombie mini-boss or a very rare super boss while you are in the city. You can play the game either in Single Player or Multiplayer mode.