Adrenaline Combos: 

Keep in mind that you have to press these key combos quickly.

Speed (makes you run faster): Forward , Forward , Forward , Forward
Booster (gives health) : Back , Back , Back , Back
Invisible (does what it says) : Right , Right , Left , Left
Berserk (makes weapons shoot faster) : Forward , Forward , Back , Back 
Camouflage (does what it says) : Left , Left , Left , Left (Requires a mutator)
Pint Sized (makes your head smaller) : Right , Right , Right , Right (Requires a mutator)