Complete "L.A. Meltdown" on any difficulty.

Complete "Shrapnel City" on any difficulty.

Complete "Alien World Order" on any difficulty.

Step in a pile of excrement.

Find a secret area.

Finish the "Hollywood Holocaust" level in under 3 minutes.

Kill every enemy on a level.

Find the Doomguy in the Level "Death Row".

Find Sam in "Mirage Barrage".

Finish any level on "Damn, I'm Good" difficulty.

Listen to Developer Commentary (Use at least one trigger).

Burn 50 bad guys to death.

Carry all weapons with ammo at once.

Kill 10 bad guys in 10 seconds while on steroids.