Contract Killer

Contract Killer is a Fallout 3 perk.

The "certain person"
You will get a note from Littlehorn and Associates telling you to go to the scrapyard. Daniel Littlehorn, the CEO, resides at the scrapyard office, and will pay 15 caps per ear.

Bounties
With this perk, the player can remove an ear from every good human or non-feral ghoul character he or she kills. The ear can then be sold to Daniel Littlehorn at the scrapyard for 15 caps and -10 Karma.

Bugs

 * Characters that are essential are also scripted as good characters (including Daniel Littlehorn) and will drop an ear every time they're knocked unconscious, for a potentially endless amount of ears.