Some good points here, ill go ahead and say straying away from the 3arc formula in general:

Stupid PAP names (Spiderbite's wet dream for example)
Non 3arc PAP names for 3arc guns (Eg Ray gun not being Porter's X2 Ray Gun)
PAP camos with lots of black on them, so it just looks horrible
Infinite damage Scavenger
Thundergun giving drops
Unlimited Ammo powerups
Godmode powerups/perks
Out of place textures/Youtuber references/anime or any of that shit
Wallguns not having chalks of the gun (Eg just the ?, or the name of the gun)
WAW wallchalks for ported guns (eg BO2 MP40 using waw MP40 chalk)
OTT custom powerup FX (Stick to the god damned green glow! we don't need a fireworks show over the Max Ammo!)
Guns moving to the bottom of the screen when you move (dodgy weaponfile movement settings cause this)
Custom round changing sound that isn't from Zombies (Good ones can be excused)
Un-Headshottable zombies (Dodgy zombie model ports, up there with zombies that revert to Nazis when losing a limb)
Unrealistic weapons (eg a colt with a 50 bullet mag that's fully auto)
Weapons sharing firesounds (can be excused where 3arc does it, eg Ak74U and MSMC)

An unpopular opinion here - Custom game modes
They are simply un needed
Sure Gun Game in zombies is cool, but one time on one map and that's it, I don't wanna play it again
Kill Confirmed in zombies? Cool idea, cool you did it, but I just wanna play survival.

And the biggie - Buyable Endings
I will never understand the love for those, zombies has and always will be about ENDLESS survival, not survive until you get 50k

In general: Broken stuff

In detail:
-Bland vision/worldspawn
-No detail in map
-Shaders, that dont match with rest (like WaW stock perks with BO2 shaders + BO1 perks with BO1 shaders)
-"Hype" maps (Maps, that get a lot of hype from Youtubers and such and then they turn out to be shit)
Just to name few, lol

People claiming that a map is as good if not better than an official Treyarch map. Always rubs me the wrong way since everytime a map has been declared as such it always tends to have issues that i wouldn't (normally) find in a Treyarch map.

Not to say that a custom map can't be, just that none of the maps so far besides maybe Das Herrenhaus even comes close IMO.

Can you dock a mapper for other people being hype? That seems a tad unfair.

Damn ProRevenge you really hate alot of things about zombies  . There are alot of interesting hates here and since Nate made a what do you hate topic, I as another Nate will make a what do you love topic 

Haha, those who play my maps will know I follow the 3arc forumla like gospel

I have quite a concise list of likes in maps too, when that topic arises

When I can't find the triggers for weapons or doors.
Weapons that are much weaker than they should be.
Auto-Colt.
Auto-colt that turns into C-3000 when paped.
Shaders not matching, in other words mixing waw perk shaders with bo2 perk shaders.
Bear hugging zombies.
Soul boxes that are in maps, just to have soul boxes.
Buyable ending that don't require any kind of object to unlock them.
Perk limit, with no way of obtaining more than 4 perks.
Barriers not being clipped, so that I can jump through them.
Having 5+ wonder weapons on 1 map.
Alternate game modes. They might be fun for people who can get co-op lobbies going, but for those of us who are stuck with solo most of the time, they kind of suck.
Blinding fx on power-up drops that make it hard to tell what the power up is.
Having limited wall-buys.
Mule kick.

People claiming that a map is as good if not better than an official Treyarch map. Always rubs me the wrong way since everytime a map has been declared as such it always tends to have issues that i wouldn't (normally) find in a Treyarch map.

Not to say that a custom map can't be, just that none of the maps so far besides maybe Das Herrenhaus even comes close IMO.

Which 'issues' exactly?

Some good points here, ill go ahead and say straying away from the 3arc formula in general:

Stupid PAP names (Spiderbite's wet dream for example)
Non 3arc PAP names for 3arc guns (Eg Ray gun not being Porter's X2 Ray Gun)
PAP camos with lots of black on them, so it just looks horrible
Infinite damage Scavenger
Thundergun giving drops
Unlimited Ammo powerups
Godmode powerups/perks
Out of place textures/Youtuber references/anime or any of that shit
Wallguns not having chalks of the gun (Eg just the ?, or the name of the gun)
WAW wallchalks for ported guns (eg BO2 MP40 using waw MP40 chalk)
OTT custom powerup FX (Stick to the god damned green glow! we don't need a fireworks show over the Max Ammo!)
Guns moving to the bottom of the screen when you move (dodgy weaponfile movement settings cause this)
Custom round changing sound that isn't from Zombies (Good ones can be excused)
Un-Headshottable zombies (Dodgy zombie model ports, up there with zombies that revert to Nazis when losing a limb)
Unrealistic weapons (eg a colt with a 50 bullet mag that's fully auto)
Weapons sharing firesounds (can be excused where 3arc does it, eg Ak74U and MSMC)

An unpopular opinion here - Custom game modes
They are simply un needed
Sure Gun Game in zombies is cool, but one time on one map and that's it, I don't wanna play it again
Kill Confirmed in zombies? Cool idea, cool you did it, but I just wanna play survival.

And the biggie - Buyable Endings
I will never understand the love for those, zombies has and always will be about ENDLESS survival, not survive until you get 50k

+1

What do you love about custom zombies? Follow this link
http://ugx-mods.com/forum/index.php?topic=10249.new#new

Nate I will add a link to your discussion in mine as well. I already have found this discussion very useful for mapping my current WIP and I can only imagine a counter part to this discussion can be beneficial as well. If you could edit your post to include my discussion that could be useful for all on the forum

Go away we want to hate on shit

- Box maps
- People saying they added detail to their maps but just spammed models
- People stealing scripts 
- CFG weapons
- Maps made in under 3 months
- Themed Maps (not as in like a space station or theme park, more like a tv show or comic)
- Maps made for specific Youtubers that the community can't play

Which 'issues' exactly?

Anything. From the assets used to the level design to the scripting.

Anything. From the assets used to the level design to the scripting.

I thought you were talking about errors, i.e. G-spawns or w/e, because those are very much issues present in 3arc maps. But funnily enough, I actually agree with you for once Daedra.

I don't like maps with no flow to them and (not AS important) no backstory. I'm not asking you, the mapper, to type out a 500 word essay on why you're at this location but give hints or at least think about it when you're doing up the map. At lot of locations such as Hospitals, Buildings, etc. it's obvious you're defending yourself, but what if I'm in a Town? Why did I suddenly stop at this town? As for flow this thing of opening doors and doors, one way maps, etc. doesn't really give me a buzz. I like to explore, and I like that feeling in zombies, take Leviathan for example, so much to explore, but it's not endless rooms with nothing to them, every room is detailed, has something to offer, and gives flow. Loops etc. also help with this.

Poorly ported weapons aren't as important to me but I don't like looking at an MP7 with a big hole going down the rail, along with lack of normal and spec and cosine maps, they give dept and appearance to the gun. Lime provides them, use them. (For ported weapons the DDS spec image, the alpha channel of that is the Cosine map, it might work 100% in WAW so a bit of editing is required).

I don't really "hate" much that people put at, yes I don't like box maps, etc. but most people ARE amateurs or are new to game design in general (however it's best to keep your test maps to yourself and off the forums, it clutters the releases section.). I feel we do undeniably attack new mappers instead of point them in the correct direction to tutorials, etc.
 
My issues stand with things (such as the holes in guns) that are easily fixable. There are gun packs (Nate's ) available, there are perk packs available, heck Harry is even doing a full bloody pack that has everything you could possible want in WaW!.

- Themed Maps (not as in like a space station or theme park, more like a tv show or comic)

A space station map sounds like the worst 

- Wrong weapon sounds
- Box Maps
- WaW Weapons
- WaW Bobbing
- Wrong Shellejects
- OP Boss
- Holes on weapons
- Tranzit Perk shaders and Power Ups
- Fake PHD Flopper
- Public Beta Maps
- FG42 fire sound that feels together with original fire sound for that weapon
- Maps with 24 Perks...
- death_reaper0 maps

I absolutely despise soul chests. I think the idea was stupid and begins to take away from the custom zombie feeling. If anything have the wolves from Mob of the Dead, but when I see a soul chest the map loses some respect from me. I also don't like when weapons don't have the right sounds. That's really about it

Even like those in Oil Rig? I think soul chests have alot of potential to be fun, but its stuffy's prefab that everyone overuses.

To me, the big issue with Soul Chests have always been how people used them. Smack it onto a map, and call it an objective. It's repetetive, and doesn't have much replayability when you always just fill in a few chests.