Commentary Mode:
Beat the game on easy or normal.

Hard Difficulty:
Beat the game on easy or normal.

Unlock Animation Show Room:
After collecting all 62 packs of smokes, including the three from the new areas with the Riot Guard, a new location called the Animation Show Room opens in the Extra Content. Here, you can watch Riddick perform all 28 of his combat moves on Johns, as well as some cool little easter eggs.

Various Codes:
While playing, press [CTRL] + [ALT] + [~] to bring up the console, then type any of the following codes:

Effect - Code:
All Weapons/Items - cmd giveall
God Mode - cmd godmode
No Clipping - cmd noclip
Unlock All Director's Cut Special Features - unlockall
Spawn Another Riddick - cmd selfsummon
Suicide - cmd kill
Switch 1st/3rd Person View - cmd cyclecamera
Load Map (#=Name) - map #

Note: On the MAP command, use the names from the Install Directory\Content\Worlds.