Junders Plunkett's finger

Junders Plunkett's finger is a unique item for those with the Lawbringer perk.

Background
After finding Bounty notice: Junders Plunkett on the body of a dead regulator, Junders can be killed, and this item can be found on his corpse. However, killing Junders is all that is necessary to unlock the dialogue option for the 1,000 caps reward from Sonora Cruz and this unique finger does not have to be looted. If looted, because it is a quest item that is never actually used, it will remain in your inventory indefinitely.

Behind the scenes
The script for killing Junders Plunkett is an automatic check, not involving the finger at all, likely meaning that it was intended to be removed from the game, but forgotten.