Overshields are for Sissies

Overshields are for Sissies is an achievement in Halo: Combat Evolved Anniversary. It is awarded for completing the campaign level The Pillar of Autumn on Legendary without picking up an overshield.

Method
It is possible to complete this achievement along with the "Walk it Off" achievement.

Simply avoid entering the Covenant boarding crafts. Due to close quarters of this level, grenades are very useful in both killing and drawing enemies out of cover. Throw grenades while still staying in cover. Burn through the Covenant using Plasma rifle on Sangheili and Pistol on Unggoy, and one will eventually get to the end of the level.