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
EDIT:
just found out about some other charms that appear in Corvo's bedroom HERE. Since they talk about "the DLC" i assume it's in the official Bethesda downloadable content (Dunwall City trials)