Respect for the Neil Cicierega, that shit's been on the rotation forever now.

Here's a couple of other notable ones on mine that may not be as popular:

Jason's Mom - Ice Nine Kills (I also recommend all of their silver scream anthology, but I fully acknowledge that their music may not be everyone's thing. The parody of Stacy's Mom is great though.)

What's A Devil To Do - Harley Poe

It's Terror Time Again from Scooby Doo on Zombie Island (Find whichever cover you like, or the original)

Salem (Burn the Witch) - Nothing More

The Hearse Song - Rusty Cage (I also love Harley Poe's version)

BRAINS! - Aurelio Voltaire (From Grim Adventures of Billy and Mandy)

Necromancin Dancin - Bear Ghost

For The Departed - Shayfer James

You Make Me Feel Like It's Halloween - Muse