Disclaimer: I dont think this thread is asking about terrible as in the dissapointing, lackluster or underwhelming games that you have played, or dare I say it: functional. No, its asking for legitimately broken, unfinished wretched games that one cannot get enjoyment from. At all.
No, Big Rigs doesn't count, one can laugh for hours at that kind of game.
In this case I'd have to pick the lowest common denominator and go with Bubsy 3D, as that eyesore almost made me go blind.