LOL! Your poll conjured up an image of the Crocodile Dundee II movie where the drug guys follow him to Australia. The bad guy (with a rifle) approaches the little guy (whose drinking a beer in the middle of nowhere) and says something like, "You don't have a gun!?" Answer, "I don't need no gun, I've got a Donk!" "What's a Donk?" And, Donk (the biggest, ugliest most inbred looking SOB in their local bar) appears and bonks the bad guy on the head.
Translate to pool scene: You're playing in a heads up money game and your opponent starts woofing and sharking you big time. You retort that you don't need to worry about his sorry ass beating you because your pool cue comes with a DONK (i.e., the biggest, bad a$$, meanest inbred looking SOB in the place)!