The Silver Shamrock Commercial from Halloween 3... I have literally no regrets about admitting to loving that song. Yes it's daggy, it's silly, the movie it's from is kind of bad but I can't help it, this song get's stuck in my head all the time.
And while we're at it, let's go with the obvious one that is kind of an ultimate in horror songs. Dream Warriors from Nightmare on Elm Street 3
Almost the entire Freddy vs Jason soundtrack , Anything - Dramarama from NoES part 4 and Cemetery Gates - Pantera from Demon Knight . Those are just off the top of my head , though I do enjoy quite a few horror movie soundtracks from guitar screaming metal to tubular bells . Music to me has always been something that grabs you by your emotions and takes you for a journey . Great question by the way .
I'm bending the rules here based on the OP's question....but I can't just help it. I loved this song and the movie. The Klowns have knives and they do hunt down unsuspecting humans in a small town....that's kind of slasher like right! lol