Below is a list of the significant helmets in Dragon Age: Origins.
Bergen's Honor
Description: When the Grey Warden Bergen knew he was at the end of his life, he descended into the Deep Roads joined by a full company of the Legion of the Dead. They slew hordes of darkspawn, clearing tunnels that had been lost for centuries. When at last they fell, a lone dwarf brought back Bergen's helm, as well as his defiant and inspirational tale.
Location: This is a massive dragonbone helmet. So it's end-game warrior fare, at a good price. Besides Corruption at the end of the game, it should be the best helm available.
Stats: Adds +2 to armor, adds +25 to physical resistance, adds +6 to attack.
Note: This is available through the Collector's Edition of Dragon Age: Origins.