PILOT-class Mjolnir

The MJOLNIR/Pilot is a UNSC Air Force helmet adapted for use with the MJOLNIR Powered Assault Armor as well as other UNSC armor systems. It entered service in the UNSC Air Force in 2541.

It's an unlockable helmet in Halo: Reach costing 90000 cR, and looks somewhat similar to the EVA and SPI helmets.

"Haunted" Helmet
The Haunted Helmet is a variant of the Pilot helmet, with no visor and a skull where a face would be. This Helmet can suprisingly be bought for 1 cR, but first you have to get every other helmet in the game(Excluding pre-order bonuses like the Recon Helmet).