Dealing with Contreras

 is a quest in Fallout: New Vegas.

Quick walkthrough
Contreras wants you to run certain errands for him, doing so will give you a unique rifle This Machine. You can also turn him in to Lt. Boyd and receive the Rifle.

Bugs
Sometimes your contact for the third errand will not show up.

The repsonces for the third errand are all messed up if you choose to kill the officer first.

After the third errand he will disappear and won't be where you previously talked to him.

When you first speak to Contreras there will be no option to start the quest, just to browse his inventory and to leave.