Although it wasn't a bug, one of the first games I wrote was Hyperball for the Atari ST. You control a spaceship and fire at a puck to score goals by guiding it into the opponents score line. I had reasonably accurate physics (I think the conservation of angular momentum was just hack rather than correctly implemented from memory), which give the masses of the ships compared the projectiles you fired meant it was better to ram the puck than to fire shots at it. So I made it so that it wouldn't ram the puck (unless the player started to do so, and which case I would up the aggressiveness of the AI). It worked well, but since it would use prediction, so it would work out how far the puck was from the ship, what the movement vectors would be when the shot would get there etc, that it was almost impossible to beat the AI. I just added a difficulty level, on hardest difficulty it would run the AI code every other frame, (it originally ran every frame), and would just run it less often on the easier levels.
All the code was in 68000 assembly language, I miss programming in assembly language now (well I don't miss x86 assembly language that much