I'm bored as hell, so here's a little discussion for us: your top 4 favorite (for any reason) custom zombie maps. Me first:
This is one of just two maps that has acually made my jaw physically drop. Starting in a hauntingly beautiful desert vista, the map soon opens up into probably the most impressive underground area ever devised, it's really something else. Tons of sprawling floors and dozens of doors in a descent to the bottom of the facility. Everyone should play it: just make sure you DON'T go past the door out of the Jugg/PPSh wallbuy room on round 9, otherwise you might crash!
2. Dead Ship
This map is a favorite of a friend's and mine: its overall campiness lends it perfectly to co-op matches. Ticking all the right boxes -- detail, weapon selection, custom perks and even voice-acted stories, Dead Ship feels like a game-within-a-game through the fantastic TMG mod.
This map flows so perfectly it's almost unreal. If I was forced to pick one map that could be passed off as official 3arc DLC, it would be Lockdown. Branching paths, quality weapons, beautiful aesthetics, and challenging difficulty with a nice little easteregg form the definitive recipe for a good time.
4. Farm Swamp
I can't really say much about this one other than the fact that it is the best looking map ever released. Seriously, just play it.