This is fully working cheats list:

Enabling the cheats:
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Sissy: Allows the use of cheat codes.

Basic cheats:
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Armory: Gives you most of the weapons in the game.

P2RInv: Gives you few weapons from P2 Ressurected.

Payload: Gives 9999 ammo on all weapons

Kamek0wnzj00: Grants all weapons, max ammo, and full health

PutYourWeedInHere: Gives you lots of M@D Weed

CrackAddict: Gives you lots of "health" pipes

Domino: Gives you lots of pizza

JerkInYourBox: Gives you lots of fast food bags

MeowMix: Gives you lots of dervish cats

Curaga: Restores health to full

BaleSomeHay: Gives you a pitchfork.

RapeStick: Gives you a Spiked Baton

Doubletrouble: Gives you Sawed-off shotgun

Superpunchout: Giver you Knucle dusters

Batterup: Gives you Baseball bat

Edweapons: Gives you weapons from Eternal Damnation

LimbSnapper: When you make a headshot with the flying sledgehammer, you will sometimes see a funny slow-motion sequence.

HulkSmash: Lets you throw an unlimited number of sledgehammers

ReaperOfLove: Lets you throw an unlimited number of scythes.

Bladey: Lets you throw an unlimited number of machetes/katanas.

MightyFoot: Grants you a super-powerful foot of kicking death.

GonorrheaChaChaCha: Gives or heal Gonorrhea (toggles)

MoonMan: Toggles Low Gravity

SuperMario: Lets you jump as high as Super Mario

Anarchist: Removes all police officers and military from the current level

PlayaHata: Bystanders hate you (persists between levels)

CopKilla: Makes bystanders randomly attack the police

Charismatic: Bystanders love you.

SonicBoom: Lets you run as fast as Sonic the Hedgehog

TheQuick: Makes all your weapons fire ten times as fast as normal

UnQuick: Turns off the effects of TheQuick

IFeelFree: Toggles noclipping/ghost mode

LikeABirdy: Toggles free flight mode

AllahMode: Toggles god mode

GhostTown: Removes all pawns from the current level

Bullet: Toggles bullet time!

Other cheats
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Heat: Toggles thermal vision.

FastRockets: Speeds up rockets (stacks).

SlowRockets: Slows down rockets (stacks).

WallHack: Toggles wallhack (you see people through walls).

Antibullet: Toggles antibullet (In opposite to bullet time, everyone gets faster)