There are Halloween costumes and then there are HALLOWEEN COSTUMES.

With animatronic eyes and a face, this Halo Covenant Elite head will most surely form the ladder. That's right, moving mandibles means you can use all caps when you describe what you're going as for Halloween.

Not a lot is known about YouTube user petemander1, the guy who is making this thing, but his attention to detail and ability to create scary moving eyes is pretty amazing.

Halo Elite Costume [YouTube, via Joystiq]