100 Serum Vials in Killer 8 mode
At the "Press Start" screen for Killer 8 mode, press Down, R, Up, L, Y, B, X, A, A. If you entered the code correctly, you will hear the healing sound. You will get the vials when you start Target: Angel. Repeat the level over with the code enabled to get another 100 vials.
Alternate ending sequence
Successfully complete the game on the Killer 8 difficulty setting to view an alternate ending sequence.
Climbing stairs faster
When your character is going up on a set of stairs and slows down, do the following trick. Turn your back to the stairs and start running, then do a quick turn as soon as you start running. You will climb the stairs faster.
Faster blood vials
When you have lots of "thick blood" and you do not want your machine to stop working with two or three conversions, tap Start + A repeatedly when the blood is converting. Do this as fast as possible and you will see the vials being produced faster than normal and with less blood.