Glitches I have tried and some I have heard of:
DS1:
Duping: duping consumables like Souls and Humanities using the brightness menu and duping of various items with the help of the Blacksmith. I never used these Glitches to level up, only to buy out merchants and to cut down on grindig Covenant items and similar things.
Other interesting DS1 glitches I haven’t performed: Force quit wrong wrap: closing the game just at the end of the loading screen sends you to the default location of the area. This for example facilitates easy escape from Ash lake or the catacombs.
There are also various Glitches to eliminate fall damage that I haven’t tried yet. On my next playthrough I’m definitely trying to jump straight down from the back entrance of Blighttown.
DS2:
I actually haven’t tried any glitches. Parry Walking looks interesting (and difficult), but I haven’t done it yet. This allows you to (with some caveats) to walk on air after parrying and then jumping on an enemy with specific timing.
Oh I also haven’t taught the Dragonrider about gravity yet.
DS3:
Tree skip. To access the upper part of the Firelink Shrine early.
Other than that? I haven’t tried any glitches.
Bloodborne:
Loot Duping. I used it for example to dupe Chunks in the DLC and Insight from Iosefka. You kill an enemy and then don’t loot them, instead you run to the loading line to the next area and repeatedly un- and reload the area. Wandering Nightmares need to be repeatedly killed for the dupe, for other loot it’s unnecessary.
A short skip in the forest: you jump by the nook with the crows over the scenery directly to the area with the cannon. I do this in higher NG Cycles.
A skip in Old Yharnam from the beginning to the end I could not pull off after an hour of trying. It was funny seeing that skip in GDQ and hearing the crowd cheering for the easy but impressive part and then not reacting to the extremely difficult jump over an invisible gap in out of bounds without visual cue.
I also haven’t tried the skip in the drawing yet. A skip based on enemy RNG wasn’t worth it (yet) and I also want fast access to the DLC through defeating Amelia. But I recently learned you also get access by defeating Rom.
Elden Ring:
Jumping into Vulcano Manor proper, after being kidnapped by the Abductor Virgin. I’m actually a bit unsure, if this is even a Glitch since the jump is so easy. This gives you easy access to, at that point, rare upgrade materials. Also you can unlock the shortcut to Godskin Noble or you can just defeat the him outright.
Using the Shackles for unintended purposes: Revealing illusory walls, manipulating flamethrowers in dungeons, unlocking spirit springs. I also jumped over some unintended geometry like getting Regalia of Eochaid early or accessing the Ruins of Unte from the back.
I also teach some Bosses about the concept of gravity: Night's Cavalry, Death Rite Bird, haven’t taught Draconic Tree Sentinel yet. The Night's Cavalry in Caelid is easy to cheese, Death (Rite) Birds are easier to defeate head on with Sacred Blade (they really don’t like jumping of). You can also backstab crit the Bell-bearing Hunter in Cealid and yeet him of, but I haven’t done that yet.
I also failed to do Renna's Rise Skip. You can jump over the tip of the tree's into the tower and access Ainsel River early. This is glitchy Fromsoft platforming on torrent. Think of it like trying to perform DS3's Tree Skip perfectly back to back 3 times without pause. Very frustrating I wasted, ugh, over 2 hours of my life on it and then I see challenge runners do that trick on their first or second try.
Another super broken Glitch is again Force Quit Wrong Wrap. You can access the capital or Farum Azula, if you perform the glitch in the preview location, without defeating a single enemy. This glitch is a bit to broken for me, but I’m probably going to have fun with it in the future.
soulsspeedruns.com is a great resource for looking up glitches. ymfah and splee5556 YouTube channels are also worth a look.