There's one on the stairway to the Tir Chonnail bank. You can get to the platform of the bank by trying to click to the right of the doorway, onto the platform pretty easily.
I also had a friend who said she fell off the platform of the soul stream where Nao is, but no idea how...
And for some reason I tend to get glitchy cutscenes for some bosses sometimes, even without mods.
And in pretty much any elevated platforms, you can get really close to the edge and sit down/up or something to have a temporary teleport/fall effect, though it doesn't do anything physically.
I've seen an elf in Dunbarton using the dice tossing skill while hiding, which looked pretty interesting... but I couldn't accomplish this myself. I'd like to know how this works, though.
Sometimes if you mount a broom pet, if it lags the animation, it will look like your character was impaled up the butt while getting on it...
Also when I tried dueling myself with the self right-clicking mod, it had that glowing ring effect that appears when requesting a duel, and it stayed there even after I left and came back. It was near Lepus in Filia.
You can change use the sitting pose for an outfit with any outfit if you just switch them after sitting down.