I always wished they would have shown Billy and Stu unmask
The whole movie builds up this masked killer and making us think "Whos behind this mask?" and the ending when its revealed who the killer is theres no unmasking or anything, just Billy flips the switch and goes crazy.
I love the movie but the one thing i would have changed would have been either Billy or Stu to be in the actual costume and take the mask off. Cause we never actually see either of them in the costume which i always felt a bit letdown by.