I think it’s been patched at this point, but I’ve used one in the Opera House in Lies of P where you could the entire level if you stood at the top balcony on the right-hand side after killing one of these spider puppet thingies and did the fable art of the Azure Dragon Crescent Glaive. It would propel you quite a stretch forward and you could launch yourself over the railing and down where you need to be to move on to the boss.

I’ve watched a lot of speed runs for Sekiro, so I know most there are in the game and have tried a couple myself. Some of these I also just recently used in my current playthrough:

• Ogre skip: very hard to pull off and not really worth it imo because the skip is harder than the boss fight, but it’s fun to attempt

• Bull skip: similarly difficult but a little easier to pull off. You can jump onto a roof that’s not intended to be jumped on and jump around a corner onto a wall that leads into the boss arena of the bull. You can just move along the walls and outside the boss arena to just skip it entirely

• Ashina Castle “interior” skip: There’s a sculptor’s idol that leads inside the castle where you need to navigate through a couple rooms and fight a mini boss before you can move on to the fight against Genichiro. If you don’t want that, you can instead turn back around to the window you climbed through to get to the sculptor’s idol and jump onto the roof to the left to skip the entire interior section and skip ahead to the Genichiro fight

• Mist Noble/forest skip: Instead of navigating through the entire forest, you can skip that section entirely and glitch your way onto the building where Mist Noble chills. You need to jump onto a tree branch, off the branch onto the roof, and then you can just jump into the building through a hole in the roof. Pretty easy to pull off and saves quite some time

• Corrupted Monk skip: Only ever pulled it off once, but it’s fun to do. If you enter the arena and stick to the left-hand walls of the arena, you can trigger her spawning without her aggroing you. If you position yourself very carefully behind her and through a number of fistfuls of ashe and some firecrackers, you can move her so far back towards you that you can jump off a nearby lantern and aerial deathblow her to skip the entire fight. Pretty fun

• Demon of Hatred skip: It’s a little tricky to pull off but ultimately more fun for me than the actual fight itself (sorry DoH apologists :D). There’s a watchtower towards the gate where you’d first move to after beating Gyoubu. You can jump onto it by double-jumping and ledge-hanging. After you did that, you can jump onto a nearby wall, once again move along the tops of the walls, and glitch DoH to fall out of bounds trying to chase you. It’s quite funny to see since it’s a giant monster leaping into its death :D The skip also works with Gyoubu, but it’s a little harder for some reason, I seem to remember.

A glitch that’s also quite notable for Sekiro is that float/dive/swim glitch (?) where you can skip a huge part of the game by just swimming through the air up to Fountainhead Palace. It’s quite funny and easier seen as a video than explained so here’s a link: https://youtu.be/xOAFBDKNVeU

There’s also a couple skips I’ve seen and used in Bloodborne, but my phone is running out of juice, so I’ll just leave it at that :D Cool question!