Lump of brain

 is an item that the Lone Wanderer finds in the Point Lookout add-on for Fallout 3. It is a piece of the Wanderer's own brain in a glass jar.

Location
The item is in the Engine Room of the Duchess Gambit, on the table next to Tobar. It can only be obtained after completing the quest Walking with Spirits and asking Nadine in the Ark & Dove Cathedral to remove your scar. It has no real use, but it can be used as a decoration for the player's house/suite.