No More Room in Hell the long awaited Source zombie modification.
This is a basic zombie survival game that even with map knowledge is still pretty difficult, actually... Too difficult. Practically all the melee weapons are outright useless and hell, even with the sledge hammer being the best melee weapon, you run out of energy really fast. And With that said, you're basically forced to use guns, but good luck finding any ammo. Could be a good game if it wasn't so difficult - "impossible" but I guess these days you can't expect free games to be good because they almost never are. <.<