I played ESF 1.2.3 for a while and didn't really find a lot of bugs, people have shown me shit that I don't think I would have found otherwise:
-generic beam circles around the pillars in Cell Games (I think everyone knows this).
-while in advanced melee if you press something like down, down-forward, forward, back+punch as the first series of key strokes as fast as you can, it's virtually unavoidable even if you press that series successfully I've seen it hit anyways.
-I've seen people telespam and simple melee someone right after throwing them. Piggy backing on that you can skipping a person across the ground like a rock skips over water, but you can follow up up with a simple melee if you're aim is really good.
-I heard of one a long time ago that if you're Frieza and you throw a Disc then go into spectator that i'll follow whomever you spectate. I'm not sure if that's true or if i just made that up... lol
takes a special kind of person to find bugs I think, I feel many people want to be beta testers for the sake of playing Final and that's about it.
There are also bugs that make you invoulnurable to KI attacks except for Kiblobs and melee, there is a bug that lets you have moves of different characters (like Vegeta having Gokus moveset and so on), there is a bug to teleport inside some, allowing you to constantly hit them with simple melee and they cant run from oyu, cause your character is glued to theirs and the list goes on.
The generic beam thing isnt a bug, its there because of the way beams work. The advanced melee combo is the result of ping, and can be avoided if you know its comming (it was known as advanced speed in the past), hitting someone with a teleport after advanced melee or throw isnt really a bug either, but a skill, allthough there is a bug that allows you to hit someone the moment you throw him.
The rollhit isnt a bug, but an exploit that sadly went unnoticed, and is produced because of the system that allows for multiple hits when bouncing someone of the terrain (thats also not a bug), but that feature gave rise to the rollhit and ceeling hit exploits.
There is a bug that allows you to instantly stop rolling on the groud, and the list goes on.
There are also a few server crash bugs you can cause with console commands and so on.