Zombie Master: Reborn is the revival of an old and abandoned Half-Life 2 mod, the mod mixes up both FPS and RTS elements where the survivors must fight through a horde of zombies and avoid dangerous traps controlled by the incarnation of evil: the Zombie Master.
ZMR is current in Beta version 1, the mod has been re-built in Source 2013 and contains various fixes to the bugs of the original mod along with a new new HUD, improvements to the zombie path finding, matching viewmodel arms, survivor AI, a new zombie selection menu and the ability for map makers to create their own custom weapons.
You can get the mod here on ModDB. http://www.moddb.com/mods/zombie-master-reborn To play it you only need the Source SDK Base 2013 Multiplayer installed.
We play very sporadically but it's pretty easy to get the server populated when the thread gets bumped. Here's the IP: 173.71.151.74:27018