Successfully complete the indicated task to unlock the corresponding achievement.

Achievement	How to unlock
Air Element	Obtain the Air Element.
Are You Serious?	Complete the game in single player on unmodified serious difficulty.
Cannon Expert	Pierce at least 10 enemies with a single cannonball.
Co-op Beginner	Complete any level in co-op.
Co-op Hippy	Complete a level in co-op with blood option set to hippy.
Earth Element	Obtain the Earth Element.
Fire Element	Obtain the Fire Element.
Fragger	Frag a total of 100 players.
Hey! That's cheating!	Trigger Ugh-Zan's regeneration.
Huge Pile of Lava	Defeat the Lava Golem boss.
I love my Cannon	Kill 100 Enemies with the Cannon.
I love my Minigun	Kill 300 Enemies with the Minigun.
I love my Rocket Launcher	Kill 150 Enemies with the Rocket Launcher.
I love my Shotguns	Kill 250 Enemies with a shotgun.
I love my Thompson	Kill 200 Enemies with the Thompson Submachine gun.
Leap of Faith	Leap into the unknown on Luxor.
Look Ma, I won!	Win a versus match.
Look, it's a secret!	Find at least 10 secrets in single player.
Metropolis King	Complete the Metropolis level in single player on unmodified serious difficulty.
Quick Draw	Pull out a single Colt and immediately deliver a killing shot.
Serious Beginner	Complete any level in single player.
Serious Co-op	Complete the game in co-op on unmodified serious difficulty.
Serious Run	Complete the game in single player by beating the estimated time on each level.
Serious Sam	Complete the game.
Wall of Bullets	Kill 20 enemies with the Minigun without releasing the trigger.
Water Element	Obtain the Water Element.