Contract Killer (Fallout Supplement)
From D&D Wiki
With this feat, the player can remove an ear from every lawful humanoid character he or she kills. This ear can then be sold to a certain person (whose identity is disclosed when you take the feat) for TUs/Caps.
Prerequisite: Level 10, Doesn't have Good Allegiance, Doesn't have the Lawbringer feat
Special: If the character has the Good Allegiance, the ears can't be sold.