Daniel is right that the majority of the worst bugs come from playing the CPU players, because those bastards love to cheat. Though I was playing a dramatic tie-breaker game against Ultima Shadow, and on checking back for my turn, I moved to take what I thought was his card and go up 7-3 with him only having one turn left. "Aha!" I thought, "Unless he can Same/Plus in one of the last two spots, I have this game won! And that is unlikely because I didn't move where he seemed to want me to move into a trap!" I patted myself on the back for being such a genius and planned my celebration party and press conference. HOWEVER, the score didn't change to register my new points and I was enraged; I watched in horrified dismay as Ultima flipped just one of my cards to tie it up, putting us into Sudden Death. I ended up losing the game and throwing my laptop out the window, apparently killing some nice old lady with 23 now-orphaned dogs. Glitches kill, people (and unlike "Help my uncle, Jack, off a horse," that sentence works both with and without the comma).

Afterwards as I rewatched the game, I realized that the card I thought I had taken was, in fact, mine all along, and the game had shown it to me as his. xD