There are a lot.
How it works is that if you are charged by the feds over ANYTHING, you will be given an offer: agree to work as an informant, and the charges will (eventually) be dropped. That's what they tried to do with Randy Weaver (of Ruby Ridge). That's what they wanted to do with this guy.
Here is a very famous FBI “Stoolie”, wonder why all his tax problems went away?
https://time.com/53389/al-sharpton-informant-fbi-mafia/