Trench Defense from the Dawnville Map Pack in World at War returns in Black Ops 1. Survive in a small trench line. Perks are earned via killstreaks. Upgrade your gun with headshots. Survive 20 rounds to unlock the game ending round or survive as long as you can/want. All of the BO1 guns you know and love, plus some custom guns. Those that played the map in WaW enjoyed it as a small challenge map. Ported it forward to BO1 to give more people a chance to play it.
One known issue is some zombies will just stand at their spawn point. I tried for days to fix this but never found the reason it was happening. You can shoot them at their spawn, or wait for them to respawn.