My current top 5 that I have played;

1. Penguin by Erebus

2. Dead Sand Elite w/ Realism 2.2 by Tom-BMX

3. Sumpf by xjimmy33 & Bluntstuffy

4. Zombie Seelow by CodMapper

5. Overrun w/ Blops Mod by Jbird 632

Maps that will probably be in a new top five once they come out and I get to play them;

Project Viking by RedSpace200

Arrival by Dr LilRobot & Jrizzo

Celtic Ruins by Fracture Studios

Excavation Site 128 & or Lockdown w/ Blops Mod by Jbird 632

Fuel w/ UGX Mod 1.1 by GrantDaddy007

Artemovsk w/ UGX Mod 1.1 by Treminaor

I've played many amazing, OK, and horrible maps, and over the years these stand as my favorites in order:

5. Anstalt Der Untoten - Team 00 (YaPh1l and Kampfschaf)
4. Yote's Lair - ZCTxChaosx
3. Airport - Nukem
2. Last Stand Christmas - Quizz

And number one, Project X - JV

Honorable Mentions:
Cage - Tom_Bmx
Nacht Der Toten Walder - Weezy428
TMG Shooting Gallery - TMG (not sure if it was one specific person or not)
Penguin - Erebus

Restrictions I used for the list were one map per mapper and the map had to be released to the public and not WIP.

Those are mine top 5 
1.Overrun
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2.Neighborhood
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3.zombie Sumpf
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4.Lockdown
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5.Last stand chrismas

1-overrun
2-Cheese cube unlimited
3-Swan
4-Piemans maps
5-Lorkeep station

Until now, those are my favorite, but they will change once new maps are released such as lockdown, excavtion site, project viking, and many others.
Also, this map is insane, try it out: zm brick shithouse

1. Swan
2. Library
3. Lorkeep Station
4. Quizz v2
5. TMG Christmas and Alcatraz