The Sky May Be is touted as "the strangest WAD ever made" according to its text file. This is not hyperbole.
It's giant and ugly, with many of the walls textures a single color, giving the level the appearance of some giant twisted Lego-block construct.
It has massive open spaces, ridiculously high platforms, and intensely aggravating narrow walkways. But these would normally constitute a run-of-the-mill bad level.
The Sky May Be takes it to the next level, indeed, to the highest level possible. Many of the sounds are replaced with inexplicable sound clips from a British TV show.
New sprites show things like a sergeant's upper torso shooting straight up when you kill it. But the coup de grace is the Dehacked patch, which completely destroys any semblance of sanity the level might have, creating bizarre weapons and enemies, the only possible point of which is to drive you insane. Play at your own risk. (Ling)
wow.wad - Paul Thrussell
This appears to be Paul's sole contribution to the Doom community, and frankly, perhaps he shouldn't have bothered.
Utterly worthless WADs, you have a name, and it is wow.wad. It's a square room, with a square pit in the middle, with a Cyberdemon in the pit. That's it. Oh, and I should mention that the walls of the pit are untextured, so it's one giant HOM.
The icing on the cake, though, is how Paul tries to pass off the error by claiming that the "plot" of the level revolves around an injured cyberdemon trapped in an "illusio-pit". It's hard for a level to get more pointless than this. (Ling)
UAC Labs - Eric Harris
No point in beating around the bush: Eric Harris made some Doom WADs, and then he killed people. One of the Doom community's greatest trials was in April 1999, when Eric Harris and Dylan Klebold opened fire in their Colorado high school and created a new culture of fear and paranoia. After it was discovered that the pair played Doom, many avid Doomers found their computer gaming habits placed under scrutiny. The WAD itself, Harris' most elaborate, is unremarkable except for a few now-chilling features. The monsters have brand-new death graphics, doused in added blood and gore. And the text file's admonition of "KILL 'EM AAAAALLLL!!!!!," which would normally be nothing more than adolescent juvenilia, carry a certain premonitory weight. (Ling)
Nuts - B.P.R.D.
Along with TeamTNT and Mordeth, B.P.R.D. has the distinction of having a map on both the best list and the 'infamous' list. If ever there was a map that took a toll on your framerate, it was nuts.wad. There is absolutly nothing to it aside from a few large square sectors, a huge deal of ammo and powerups and an absolute insane number of monsters.
Think of a Doom map with a large number of monsters. Now double that number. Now double it again. Now make all those into Cyberdemons. Now add that same number but make them all Arch-Viles. Okay, I think you get my point. Nuts is insane.
The author also released two sequels, but neither had quite the impact the first nuts carried with it (though they are both arguably better maps than this one). Either way it's worth checking out if for nothing else than to watch Doom slow to a crawl like you've never seen before. (Cyb)
Evilution - TeamTNT
Evilution, as many Doomers know, was a TeamTNT creation which was postponed a scant few hours before its scheduled release when John Romero emailed the authors asking about a publishing deal. TeamTNT said yes, and one-half of Final Doom was instantly born. What most of them don't know, however, was the controversy that swelled up following this announcement.
In late 1995, the hub of Doom discussion was on the Usenet newsgroups, and a quick traipse through Google shows that after the "PR coordinator" for TeamTNT released the news that Evilution was postponed and possibly to be commercialized, a massive flamewar broke loose.
The online Doom community was fairly small compared to the game communities of today, and the posts that followed showed Doomers splitting into two camps: those who were delighted that amateur WAD authors were going pro, and those who derided the group as "sellouts" and "liars." The controversy quickly died down, but the scars still remain. (Not really.) (Ling)
Gothic99 - Matt Dixon & friends
Good lord. I mean, just, what in the world was Matt Dixon thinking? He was known for some quite pretty maps in the earlier Gothic DM compilations, but apparently his fetish for extraneous detail grew to an uncontrollable size.
Download this WAD and load up the first level. Underneath the 18 billion sectors, where every 3 inches there is another nook or inlay or filigree, this level is basically a remake of Doom 2 Map01. However it runs at about 1% the framerate and no one in their right mind would ever, ever, DM on it. I hope that this WAD was meant as some sort of experiment, to see just how overboard people could go with pointless detail. (Ling)
Imp Encounter (SE) - anonymous
The dark, seedy corner of the Doom level archive was always the "xxx" directory, which everybody snuck into at one point or another when no one else was looking, to see just what titillations could possibly be coaxed out of the Doom engine. Well, this WAD is not one of those titillations. Unless having sex with imps is your idea of titillation. Yes, you read that right. Not only does this level not even let you play anything -- it's really just a cutscene -- it quite graphically shows the Doomguy, er, coupling with a spawn from hell. Whoever made this level, thanks a lot. (Ling)
Mockery - Scott Cover
Mockery itself is a fairly simplistic 1998 WAD by Scott Cover to demonstrate many of the errors novice Doom level authors make. While this is nothing outrageous, people latched onto the idea and soon a full-fledged Mockery megawad was in the works.
The website still exists; a perfect time capsule of 1998 sensibilities, but the project was never finished (again, a perfect mockery of the many ill-conceived Doom projects with oversized ambitions and not enough talent). Mockery's real "contribution", if you can call it that, was to be the first "joke WAD": a sadly expanding subset of Doom levels with no particular value past making an often tiresome joke.
Source ports like ZDoom allowed authors to script their joke WADs, making them even less playable and more annoying. Certain joke WADs, like the previously mentioned Imp Encounter, do manage to elicit a laugh or two, but the vast majority are nothing more than one or two vaguely humorous notions wrapped up in a long, tedious slog of a level. (Ling)
SLIGE - Dave Chess
I had some qualms about adding SLIGE to this list. As far as random Doom level generators go, SLIGE is easily the best; none of the handful of other level generators can come close to its quality. But herein lies the rub: the SLIGE levels are good enough that some less skilled level authors might consider them worthy enough to, well, claim as their own. Soon after the release of SLIGE in 1998, the /idgames archive put a ban on SLIGE-generated levels, as a trickle of WADs with the distinct SLIGE style annoyed curious downloaders. To this day, an occasional author will get the idea that people would want to play a WAD made up of slightly modified or enhanced SLIGE levels. Now, as then, if people wanted to play computer-generated Doom levels, they would make them themselves. (Ling)
Mordeth E2 - Gaston Lahaut
If it took me as long to write this summary as Mordeth episode 2 has been in development, I would finish up sometime in 2010. The original Mordeth was released in early 1997, and work on the second episode started shortly thereafter.
Promising screenshots were released before the end of 1997 and everyone expected that the wait would not be, well, excessive. However, Mordeth E2 (and E3, which was later added in for release at the same time) suffered innumerable setbacks in the form of team members leaving, level redesigns, engine changes, and many of the assets being physically stolen when a thief made off with the computer they resided on.
It is easily the project which has been in "active" development the longest, and while an eventual release is probable, when that may come is anyone's guess. (Ling)