The interpreter for a CAD/CAM geometry processing language (P1 = 10,10; P2 = 20,20; L1 = P1,P2; - that sort of thing), written in Microsoft BASIC Professional Development System (PDS), with minimal length variable names (it ran out of single letters quickly, so moved on to double letters. PP, PQ, PR, anyone?). And, to be fair, some comments. In Italian.
Funnily enough, it actually worked, and I was able to add some functionality to it, but it was like amateur dentistry - painful, and certainly not recommended...