This is a detailed credit list with the information I could gather.
If you are going to take stuff from this mod, give credits to me/whoever created it.
Resources made by me are also listed.
Unlisted resources are likely to belong to people unknown.

//Player sprites
Firing and moving sprites, Meatshields, wounded marine, jumping, rifle bashing, by Sgt Mark IV
Weapon skins based on Marine Skins by Vader
Guarding position by Das_M
Player deaths (XPL1*, XPL2*, XPL3*, XPL4*, XPL5*, XPL6*, XPL8*, PLAY I - N, MHEA*, HPLA*, PBUR*, PMET*, PLDHA0) by Sergeant_Mark_IV
Extra rotations for PLAY  A - G by Adrian Carmack, provided by John Romero
Marine - No Weapons (PLA1*) by Captain Toenail
Marine - aiming down the sights (MAR2*) by Sergeant_Mark_IV
Cheering Marine MWAV A to F by Unknown
Cheering Marine MWAV I to N by Das_M, edited by Sergeant_Mark_IV
Generic Burning Man (BUR2*) from Strife by Rogue Entertainment
Marine - kicking animations by Sergeant_Mark_IV (edited from Captain Toenail unarmed marine sprites)
Marine - Combat Roll Animation by Sergeant_Mark_IV (edited from existing player crouch sprites by Skulltag Team)
Muzzle effects (PLMZ*) Sergeant_Mark_IV (edited from Aliens Trilogy)
Captured Marine by Sergeant_Mark_IV
Executions/Fatalities by Sergeant_Mark_IV

//Weapons

Pistol (PISR*, PISG*, PISF*) Sergeant_Mark_IV, reloading frames base by Adrian Carmack, provided by John Romero.

Axe sprite by Mike12, animated (blood smeared versions included) by Sergeant_Mark_IV

Chainsaw by Mike12, animated by Sergeant_Mark_IV

Minigun Extra animations for barrels by Perkristian and Minigunner, Ammo Belt by Mike12, base by Skulltag Team, animations and muzzle by Sergeant_Mark_IV

Assault Rifle (RIFF*, RIFFR*) Mike12, animations and muzzle by Sergeant_Mark_IV
Assault Rifle Iron Sights (RI2G*) Crucux Duo, edited by Sergeant_Mark_IV

Shotgun Base (SHSL*) by Mike12, Foregrip by JoeyTD edited by Mike12, muzzle and animations by Sergeant_Mark_IV 
Shotgun Pumping frames (SHTG*) by DoomNukem

Super Shotgun by Tomtefars and Azona, extra sprites by Perkristian, animation and muzzle by Sergeant_Mark_IV

Rocket Launcher base by Eriance, edited by Sergeant_Mark_IV. Ammo barrels from Necrodome.

Rocket MISL* by FreeDoom team

Grenade Launcher base sprites by Nmn, animated by Sergeant_Mark_IV, grenades based by FreeDoom team, animated by Sergeant_Mark_V

MG42 based on a screenshot from Call of Duty, edited by Sergeant_Mark_IV

SMG by Sergeant_Mark_IV, based on the Alpha Doom SMG sprites.

Machinegun by Sergeant_Mark_IV, based on the Alpha Doom Machinegun sprites, reload frames based on a sprite from Platoon mod of Duke Nukem 3D.

MP40 by Apogee Entertainment, edited by Sergeant_Mark_IV, side frames by Marty Kirra.

BFG9000 Sergeant_mark_IV

BFG10000 by Eriance

Taunt sprites Sergeant_Mark_IV

Mancubus Flame Cannon by Mike12

Barrel being carried by player on HUD by Mr Enchanter
Cacodemon Eye Trophy by Kamijou

Revenant Missile Launcher (RVCG) base from Hacx, edited by Mike12

Plasma Gun Based on a 3D model by Sitters, sprites by Sergeant Mark IV

Smooth Classic Doom weapon sprites by Perkristian

//Monsters
Zombie scientist by scalliano, extra death animations by Das_M

Zombies animations killed by shotgun, railgun, axe, explosives by Sgt Mark IV
Zombies animations killed by Minigun by Mike12

Shotgunguy firing and pumping shotgun animation by Sgt Mark IV

Minigun Zombie by Das_M
Minigun zombie frontal death frames by David G, gory versions (losing arm, head, etc.) by Sgt Mark IV

Zombie gibs by Sgt Mark IV

Imp dying with guts hanging out by Dr. Doctor
Imp deaths (head exploding, losing arm, burning, losing leg, killed by shotgun, rolling downstairs, cut in half, gibs for head, arms and legs) by Sgt Mark IV
Imp deaths by Minigun by Mike12
Imp leaping attack and swimming animations by Sgt Mark IV



Pinky demon eating stuff from the floor by Sgt Mark IV
Pinky demon death by losing its arm by David G.
Pinky demon deaths (cut in half, head exploding), head, leg and arm gibs by Sergeant_Mark_IV
Pinky demon plasma death by Mike12
Pinky Demon without arms by Sergeant_Mark_IV
Pinky Demon death by BFG by David G.

Lost Soul without flames and death piece particles by Jekyll Grim Payne

Juggernaut - Base, ripped from Quake 2' Tank boss model by DRUMASTER, mancubus part by 

//Decorations
Green trees by Doom_Jedi
Bush and grass sprites from DN Platoon TC
Burning tires, rubble, destroyed signposts from Terminator Skynet.
Destroyed light post by Sgt Mark IV, made from a model by Sitters.


//Gore
Blood decals, blood sprites, generic gibs by Sergeant_Mark_IV
Blood splatter effect (BLHT) sprites based on effects from TF2, edited and reshaded by Sgt Mark IV

//Effects
Large fire particles (when burning trees) by Ashish Yadav, converted into Doom by Sgt Mark IV
Rocket explosion fire particle from Quake 3
Most explosions are from common 90s effects seen in thousands of games and movies, hard to find the creators of it.
Huge water effect when exploding stuff on the water/blood/nukage - based on some sprites from Metal Slug.
Effect when shoting the water based on the effects from Blood (+particles based on stuff from Heretic)
Lava splash effects - Sgt Mark IV

//Voice Acting
Zero X. Diamond (Doomguy), Tiberium Soul (Marines), Halo 3 (female player)

//Tanks
3D Models and textures by Sergeant_Mark_IV
Cammo pattern, tracks texture from Action Doom by Scuba_Steeve
Tank Cannon HUD is based on one of Eriance's weapons, edited by Sgt Mark IV
Artillery Tank's HUD is based on sprites from Necrodome.

//PSX Doom Maps
fenderc01, Dragonsbretheren

//Extra Code
Solarsnowfall (Third Person Camera script)
Jekyll Grim Payne (base for torches)
Nash - I remember I took something from him, I don't remember what.
TerminusEst13 - The tracer code used on large tracing projectiles, such as the Artillery Tank autocannon.

//Misc
Female player mugshot sprites by Xaser
Full Helmet HUD by DoomNukem

P.S.: Some people constantly change their names.
Eriance is also reffered as Marisa Kitsune, Mike12 is also reffered as HorrorMovieGuy and HDoomGuy, David G as IsNatureToDie, and Zero X. Diamond as Chinese Tony Danza