Sgt. Daniel Contreras

 is a supply merchant in Camp McCarran and can be found in the far end of Concourse area inside the Terminal Building. He also deals in shadier businesses, where it is implied he is making chems on the side for money among other things. Contreras will give you unmarked quests that are fairly easy to complete. Depending on your choices in the unmarked quest concerning inconsistencies in the the base's weapon ledgers, he may give you the unique rifle This Machine.

Appearances
appears in Fallout: New Vegas.

Bugs

 * If you talk to Contreras during the NCR quest I Put a Spell on You, Contreras will not have the option that activate the unmarked quest to retrieve This Machine. (Needs confirmation)