Various sources (see below)
Cory Whittle for his "Immoral Conduct". The first DOOM weapons mod. Note for the newcomers out there: check out the full-featured EDGE version! (icd-se.zip)
Marty Kirra for the improved sniper rifle sprites (from Tainted Decorum by TheDarkArchon)
Zero Prophet for the pistol zombieman and player sprites (Zero Tolerance)
DBThanatos for the shotgun marine sprites (AEons Of Death 2.4)
Rogue Software for the uzi soldier sprites (Strife)
Richard R. Ward for the custom status bar skin base
WildWeasel for the 'Flynn Taggart' extra set of HUDs
Banjo Software for the counters font (HACX)
Zero Prophet for the mugshot graphics and custom font (Zero Tolerance)
id Software for the custom player sounds (Quake)
WildWeasel for the custom color palette (The Stranger)
Marty Kirra for the custom shotguns sprites (The Works)
WildWeasel for the custom assault rifle sprites (Magnum Opus)
for the Q3A-style gore effects
Xaser for the target lock system
The FreeDOOM Team for the custom teleportation effect
DoomNukem (with WildWeasel bits) for the HUD acting as base for the 'John Grimm' extra skin
Namco for the 'John Grimm' skin sounds (Tekken 3)
Reinchard for the high-resolution 'John Grimm' mugshot
OSJClatchford for the custom explosive barrel (OSJC modification v2.0)
The Zombie Killer for the particle-style bloodsplatter effect (Zombie's modification)
...and again, Cory Whittle for the Assault Battery graphics (dtcog40.zip)!