7. The Scalping Machine (Saw IV)

The scalping trap is one of the least-mentioned traps when it comes to the Saw franchise, but it really is a terrible, terrible trap. The trap pulls Brenda’s (Sarain Boylan) hair back into a set of gears. The moment her forehead splits open and the blood sprays is one of the best (and most disturbing) visual gags the franchise has ever done.