Warning - this glitch can wipe your save files. The setups shown here appear to be safe, but the risk is there.
By using a Text Warp to get out of bounds, and selecting a specific OOB tile on the map, the game will do an incorrect jump to code it shouldn't be executing. This causes the US version to go haywire and start overwriting memory all over the place. The most useful application of this, is to spawn Veran and warp to the final battle. The PAL and JP versions don't have the same useful effects.
This glitch will not work at all unless you've visited the rightmost screen in the secret passage in Ambi's Palace, or the underwater area below it.
There are many other things this glitch can do. Its effect can be manipulated primarily by the positions of sprites on the screen, and various game flags.
After starting the fight with Veran, you can activate the glitch again to skip battling Veran. This is a bit slower than actually fighting Veran if you have good RNG and you one-cycle her.
Even when veran's dying textbox appears, there are a few ways it can fail afterwards. So, when this skip is used, timing ends after the screen fades to white.
This skip makes use of the positioning glitch, which has a catch (see below).
By having a sprite at a specific x-position, you can corrupt your ring box and gain access to hundreds of rings, many of which are duplicates. The most useful is the red ring. In order for this to work properly, the present top-left area of Symmetry City must be blacked out on your map. Talking to Vasu with this ring box will crash the game.
You can use this glitch to stick link at the left end of the screen, allowing him to fly across the map. Despite being stuck on the left side, he can move screens right as well. This is a minor shortcut to dungeons 7 and 8.
This glitch depends on a flag set early on in the game, when you get the seed satchel. It is more useful if the satchel fell on the left side of the screen. In addition, the ember or pegasus seeds must be loaded in the seed shooter, or it will crash.