The Elder Scrolls III: Morrowind.
That's the glitch. Everything about that game was incredible, yet insanely glitchy.
BAD: Once, after becoming a werewolf in Solstheim, I traveled back to Gnisis on the homeland and BAM, all of the buildings and people were gone and all that was left were floating doors. This never reverted, so the city was permanently gone.
GOOD: If you "walk off" of the edge of one of the highest tiers on any of the Vivec cantons, you take no fall damage, but if you jump at a low[ish] level, you die.
GOOD: Randomly walking in Solstheim, you may instantaneously warp a good 50 feet up in the air and continue walking slowly downwards until you touchdown on the ground. This was a great glitch for avoiding them **** Spriggans and Rieklings.
BAD: Take a bunch of skooma and moon sugar and try jumping in the East Empire Trading Company headquarters in Ebonheart. Your head will forever be stuck in the ceiling (from excessive drug abuse?).
GOOD: Jump onto a desk, then jump at the ceiling. Your head will clip through and in that split second that your head is no longer in the building, no NPC can notice you as they are programmed to read the face model, so you can technically steal anything below you unnoticed.
I could name tons of more glitches from that game..