Titan

The Titan is a player class which specializes in armor and heavy weaponry. The first Titans built and defended The Wall which protects The City. Titan heritage is rooted in strength, sacrifice, and mercilessness.

Titans can be distinguished by their full body armor and swept-back helmets.

Abilities
Titans have been shown to have a "shockwave" attack called Fist of Havoc.

Design and Inspiration
During a Bungie panel at GDC 2013, Bungie stated that the Titan class is meant to be reminiscent of the classic "future soldier," citing as influences Master Chief, Storm Troopers, and other "space marines" from science fiction.

Speculation
Titans appear to have heavier armor that may grant more protection than other player classes.