Leo (Fallout: New Vegas)

Leo is the name of a possibly fictional character mentioned by Lily Bowen. It is, at this time, impossible to say whether or not Leo is imaginary, a product of Lily's Stealth Boy-induced schizophrenia, or if he is someone she actually knew once, possibly from before she was dipped.

Behind The Scenes
Leo could be a reference to a Manhunt 2 character called Leo where he affects the Daniel Lamb (the main character) the same way Lily is affected.