PILOT-class Mjolnir

The Pilot helmet is a UNSC Air Force pilot helmet adapted for use with all UNSC armor systems, including the MJOLNIR Powered Assault Armor. It entered service in the UNSC Air Force in 2541. It has an appearance similar to the EVA and SPI helmets.

It is an unlockable helmet in Halo: Reach and costs 90000 cR.

"Haunted" Helmet
The Haunted Helmet is a variant of the Pilot helmet. It is visorless and has a skull where the face should be. This helmet can be bought for 1 cR, but only after obtaining every other purchasable helmet base.

Another theory towards unlocking the Haunted permutation of the Pilot helmet involves Halloween, as the description is, "Happy Friggin' Halloween!" Nothing is confirmed at the moment, but we'll be sure to update this when it is.