While playing a game, press T for the "Talk" feature, then enter one of the following codes to activate the corresponding cheat function:
| RESULT | CHEAT CODE |
| God mode | mpgod |
| Full ammo, armor, and health | mpkfa |
| Full health | mphealthy |
| Full ammo | mpammo |
| Full armor | mparmor |
| Clipping mode | mpclip |
| Toggle coordinate display | mppos |
| Change camera angle | mpcamera |
| Change lighting | mplightscape |
| Displays your coordinates | mpwhereami |
| Increased power; more gore | mpbeefcake |
| Kill all monsters on level | mpkillemall |
| Increased speed | mpspeedup [1 - 5] |
| Increased strength | mpstronger [1 - 5] |
| Change character model to Caleb | mpcaleb |
| Change character model to Ophelia | mpophelia |
| Change character model to Ishmael | mpishmael |
| Change character model to Gabriella | mpgabby |
| Beretta; repeat for dual weapon | mpberetta |
| Submachinegun | mpsubmachinegun |
| Flaregun | mpflaregun |
| Shotgun | mpshotgun |
| Sniper Rifle | mpsniperrifle |
| Howitzer | mphowitzer |
| Napalm Cannon | mpnapalmcannon |
| Singularity Generator | mpsingularity |
| Assault Rifle | mpassaultrifle |
| Bug buster | mpbugbuster |
| Minigun | mpminigun |
| Cobalco Laser Rifle | mplaserrifle |
| Tesla Cannon | mpteslacannon |
| Voodoo Doll | mpvoodoo |
| The Orb | mptheorb |
| Life Leech | mplifeleech |
| "Brian L. Goble is a programming god!" | mpgoble |
| "Jim Totaro is da man!'" | mptotaro |
| All items | mpgoshopping |
| Health increased by 25 | mpnicenurse |
| 300 health | mpreallynicenurse |
| Invisibility | mptakeoffshoes |
| Ward (25 armor) | mpward |
| Newcroward (100 armor) | mpnewcroward |
| Willpower power-up | mpcarbonfiber |
| Triple Damage power-up | mpherkermur |
| Extra weapon selection | mpbeansofcoolness |
| Unknown | mpscorpio |
| Unknown | mpsuperzug |
| Unknown | mphideme |