Someone who performs the act of fellatio (oral sex on a man). A penis can be referred to as a 'knob'
That fuckin' knobgobbler wanted to go down on me!
A man who gobbles on the circumsized end (knob)of another mans schlong while making a gobbling noise like a Thanksgiving turkey
Mmm of love sucking on yer knob billy... gobble-gobble-gobble! I am a good old-fashioned knobgobbler!