One for My Baby

 is a quest in Fallout: New Vegas.

Quick walkthrough
Talk to Boone. He will mention his wife during conversation. Offer to help. Ask No-bark about Boone's wife. He will mention the Dino-Dee-Lite lobby. Sneak in at night and obtain the a Bill of Sale from the safe behind the desk. Ask Jeannie May Crawford to see what is in front of the Dinosaur. Put on your Baret and lead her there. Go back to Boone. After you complete the quest you can ask him to join you and he becomes your companion. He is very useful in combat using a powerful sniper rifle. He gives the Spotter perk when he's with you.

Bugs
-If you sneak in to the lobby and take the receipt before taking the quest the game won't recognize that you know who sold Boone's wife and will render you unable to finish the quest. No known solution except loading to an old save file.