please help me find out the name of this movie

[marmielake]

ive been trying to remember what this movie is called. basically there was a crazy motorcyclist who cut this guys head off and put it in the toilet and in the end it turned out to be a girl killer. also she used a big ass butcher nice to cut the head off. and when she busting in to kill there was this music like dunnadanunnadunna etc etc
it was so funny!