He sent a $1,000 check as "collateral" to some online "bank" to get a $10,000 "loan". I explained to him that this isn't how any of this works and he just paused and said, "Huh, so should put a stop payment on the second check?" He had sent them another $1,000 as some sort of second round of collateral for the loan or some other nonsense.
And I've known dumber people than him.