Sgt. Daniel Contreras

 is a supply merchant in Camp McCarran and can be found in the NCR Supply Room. The Supply Room is accessible from a far end of Concourse area via a terminal tunnel.

 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.

NOTE: After you have obtained This Machine by reporting him to (Lt.) Carrie Boyd, Contreras will no longer be present to sell supplies. *need confirmation* There will not any merchant replacing him in Camp McCarran.

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)