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 2, 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 have some people playing on the custom server right now. Here's the IP: 173.71.151.74:27018