A MegaCollection Kits
★ marks things I personally have played and recommend. Please let me know of anything else I could add in the comments at the bottom.
Ken Silverman's FPS engine wonder
Big Three: Duke Nukem 3D, Shadow Warrior, and Blood.
Raze Compatible: PowerSlave/Exhumed, Redneck Rampage (Expansion: Suckin' Grits on Route 66), Redneck Rampage Rides Again, NAM/Napalm, World War II GI (Expansion: Platoon Leader)
Others: Witchaven, Witchaven II: Blood Vengeance, William Shatner's TekWar, Redneck Deer Huntin', Extreme Paintbrawl, Ion Fury, A.W.O.L. (Steam), Electric Highways
Raze can run all the games listed above, backed by GZDoom and the other source ports below. Here's how to setup the games. Raze Touch is an Android port. Nuke.YKT also made some engines, such as PCExhumed for PowerSlave/Exhumed and Rednukem for the Redneck Rampage series, Duke Nukem 64, and some others. BuildGDX is Java-based and can run the most games.
bMouse fixes the mouselook in the DOS versions of BUILD games. Build Engine Randomizer can scramble enemies, items, and more, for multiple games.
The lifelike armageddon, when realism was novel
Duke It Out In D.C., Duke Caribbean: Life's A Beach, Duke: Nuclear Winter
EDuke32 is the de facto port of choice. All the modern mods use it. NetDuke32, for multiplayer, seems to be here.
Shaky Grounds pushes the engine to its limit. Nuts is just a ton of enemies and ammo.
For multiplayer, StrikerDM is a Dukematch Mod and Community Map Pack.
There are 3 massive projects as big as an entire game. Alien Armageddon ★ is the penultimate mod, with may, many additions, such as a shop, levelling system, randomizer, and 2 new episodes, including Space Gladiators, a campaign based on multiplayer matches against the AI. WGRealms DEMON THRONE is an amazing fantasy-isekai total conversion (Related: WG Realms 2: Siege Breaker, not sure of the difference between the two). The AMC TC is a dizzying conversion with an XCOM-style research system and very varied missions.
Legacy Editionadds in beta content and remixes the game. Blast Radius is another big project that adds 14 maps and new aliens. The Ultimate Build Engine Aesthetics Pack is a bunch of audiovisual enhancements. This EDuke32 Addon Compilation contains 100+ addons preconfigured for EDuke32. Duke Nukem Forever 2013 is an attempt to right the infamous failure, based on the 2001 trailers of what could have been. Duke Plus adds a few new features like ledge grabbing. War of Attrition adds a levelling system and some other stuff. Naferia's Reign: Invasion of the Dark Mistress adds RPG elements and multiple characters, including Bubsy the Bobcat. Blood Weapon Mod is a weapon replacement. Starship Troopers TC is impressive considering it was made before EDuke32. Duke Forces blends Star Wars stuff. Features the phrase "Darth Nukem". DNF2001 Restoration Project is a rebuild of the leaked 2011 version of Duke Nukem Forever. WG Mega Pack is a map pack with 3 episodes and more worth of levels.
Dukeworld hosts all the classic files, as well as EDuke32. Mikko Sandt's Duke Nukem 3D Site also has a list of maps. Come Get Some! reviews them.
Mapster32 (wiki ref) comes with EDuke32.
Duke4.net, Fissile Materials, SwissCM, High Resolution Pack, Legacy Of Grabbag (song) (alt link)
Twitter: Duke Smoochem development thread (very big)
The orientalist adventure
Twin Dragon, Wanton Destruction
SWP is an option, as is VoidSW.
YANG - Yet Another Netplay Guider
The gothic massacre, dark king of the 3
NBlood is by Nuke.YKT and based on EDuke32. NotBlood is a fork that tweaks the game a little, including some ways that make it easier.
The Fresh Supply remaster on Steam and GOG are also worth a shot. They're in the Kex Engine.
Death Wish is the best one you can get. Eviction is another choice.
This Twitter thread has a whole lot of recommendations. One Unit Whole Blood Launcher can install almost every mod. It's outdated and difficult to run, so I only include it as a curiosity.
XMAPEDIT is the original map editor, enhanced.
The Bloody Repo
Ken's Site, Build homepage, Build Source Code, JonoF, M210
Background taken fron here.
Suggest more in the comments!