Take those pesky guards, for instance. MGS2 offers up a smorgasbord of options to avoid or take out your enemies, including tranquilising them in the gonads, distracting them with noise, or straight up somersaulting into them. One player has found out, however, that if you're particularly determined to complete a non-lethal run of the game, you can recruit a few seagulls to send your foes packing (thanks, Automaton).
Well, we say "recruit"... you'll see what we mean:
Yes, as highlighted by BadHumans on social media, if you're able to line up your shot just right, you can tranquilise a seagull so that its limp body comes crashing down on top of a guard, thus taking out two birds with one, uh, tranq dart.
It doesn't seem like the seagulls "follow" the guards (in which case, we probably would have discovered this a lot sooner), but rather you'd need to either learn their flight patterns and patiently wait until their paths cross with the guards below, or you simply leave it in the hands of luck.
It's difficult to imagine that no one had stumbled across this in the decades since MGS2's PS2 launch, but it's certainly the first time we've seen it in action. If you want to try it out yourself, then you can with the HD re-release on the Switch eShop. Released toward the end of 2023, we awarded it a score of 7/10, praising the story and gameplay, but criticising the reduced frame rate and fiddly mechanics.