Leon

"Each one of these marks is for a past attempt on Hightower's life. I bagged each and every one of them."

 is Daren Hightower's personal bodyguard in the Heights district of the Hub in 2161.

Background
He decides who does and does not see Mr. Hightower.

Quests

 * Dispose of merchant, Steal necklace from the Merchants: For both quests, Leon protects and watches over Daren Hightower.

Other interactions
Leon will gruffly converse with the player, but he's not exactly useful for information. If Mr. Hightower yells for the guards, the player is personally kicked out by Leon.

His only function is to be the deadliest guard Hightower has.

Inventory
He has five marks on his 14mm pistol, supposedly representing five people who wanted to kill Mr. Hightower that he killed.

Appearances
appears only in Fallout.