guiltmug
verb: To do someone a favor when they did not ask for it, expecting money or favors in return.
I was on my way into the convenience store when that bum guiltmugged me by holding the door open.
I was stopped at the red light when a bum guiltmugged me by cleaning my windshield.
I was stopped at the red light when a bum guiltmugged me by cleaning my windshield.