if you preordered Dishonored with **'Arkcane Assassin Pack'** (from Gamestop) and/or **'Back Street Butcher Pack'** (from Amazon), you get access to 6 special bone charms, available in Corvo's room.

>     Void Channel: Corvo's supernatural abilities last longer and do more damage
    Gutter Feast: When Corvo eats a white rat, he regains mana.
    White Rat Friend: White rats are neutral towards Corvo, not hostile. 
    Fencer: Win sword vs. sword contest more frequently.
    Blast Resistant: Damage from explosions reduced slightly.
    Fire Water: Shot whiskey bottles explode with greater intensity. 

source : [IGN][1]


  [1]: http://www.ign.com/wikis/dishonored/Bone_Charms