Three-Card Monte

Three-Card Monte is unfindable in the original game, but can be found in Killap's Restoration Project.

Killap's Restoration Project Features
Three Card Monte can be found near the entrance to Second Street. He is found with a few people near a barrel-fire. One of them is his bodyguard Rico. If you talk to him, he will ask if you would like to gamble. After accepting his offer, he will tell you to pick a card. If you pass a Perception check, you can see that he has kept the card under his arm. If you tell him that, and go too far, he will become hostile.

Ending the scheme
You can steal his deck of cards, after which he will tell you "Sorry I lost my deck of cards".

Upstairs in the Desperado Casino, on one of the shelves, is a pack of marked cards. If you swap Monte's cards with this pack, you will gain 100 exp and will automatically win every game of cards you play with him, until he runs out of money.