During my last playthrough of Alien Isolation, I was on fire for two full missions. I don't mean I got through them quickly or managed to stay a step ahead of the Alien the whole time. I mean I was literally on fire, and so was all my stuff. My guns and melee weapon were constantly covered in flames, I trailed sparks behind me wherever I went, and I lit up every air vent and locker I hid in with a warm glow, like a walking campfire.
Naturally, this was all one big glitch: I accidentally walked Ripley into a pile of burning rubble and lit her on fire, but the flames never disappeared even after she patted herself out. So the game was pretty sure I wasn't on fire anymore, because the flames didn't hurt me or make me more visible to enemies, but the graphics took a while to catch up. And it made everything so much better.
I don't mean Isolation’s boring - it was easily one of the most suspenseful games of 2014, so it didn't need my spontaneous combustion to liven things up. But being inexplicably covered in painless fire made the game's most mundane parts unintentionally hilarious. Even opening doors or crouching in closets became an amusing reminder that yep, I'm still on fire.
That doesn't just apply to Alien Isolation either - though they usually involve less fire, finding harmless yet funny glitches always makes me happy. Healing a wounded Parisian in Assassin's Creed Unity by bumping into him (which set his 'pain' animation to 'standard', making him stand right up), or watching a spasming tiger cartwheel into the sunset in Skyrim takes moments that could've been otherwise unremarkable and makes them into game-defining snapshots of mirth. I wouldn't have remembered those parts of the game five minutes later if all had gone according to plan, but those silly glitches stick in my mind months, sometimes even years after the fact.
I don't have the same love for glitches that ruin the game (getting trapped between a tree and a rock in Assassin's Creed 3 was funny until I realized I couldn't get out and had to start my mission over), because that negative effect on my gaming experience overpowers the positive. But when it's just a graphical glitch that bathes my character in fire and gives me occasion to shout "BOW BEFORE THE QUEEN OF THE GREAT FLAME!" at my confused roommates, I feel nothing but joy at its existence. In one innocent and silly move, the game makes itself more memorable and will keep it in my heart far into the future. It'd call that a success, even if it was by accident.