Kill 25 Ork Nobs.

Retrieve the Power Source.

Get 100 Headshots.

Destroy the Orbital Gun.

Multi-kill -- 5 enemies with 1 Frag grenade.

Kill 100 enemies.

Fish perfectly 20 times by pressing the icon as it flashes.

Sneak through the underground passage without tearing your scarf.

Craft the Fire and Ice Bows. (Single Player Only)

Finish one of Gimli's opponents as Legolas in 'Helm's Deep'.

Throw Gimli 30 times.

Walk into Mordor.

Complete 'Mount Doom'.