Here is the full list of all 21 CRAZY GUY achievements.
Start the game.
rip
Flip the table!
Kill the first!
Kill the second one!
Kill the third!
Kill the fourth!
Kill an elite fighter!
Destroy the ball.
Pick up the Revolver.
Pick an ultrasound.
Pick up Blaster R-300.
Pick up Blaster R-150.
Pick up Pistol.
Pick up the Space Nail Gun.
Pick up the Laser Blaster.
Pick up RPG 2000-10.
Use medicine.
Use a grenade.