In Emerald only, the Pomeg Berry was glitchy, if used correctly. Basically, if you had a Pokemon that had HP evs and used a Pomeg berry on it and it had 1 HP left, it would either make the Pokemon's HP reach zero, or become a negative number.
People have used this glitch to do many wild things, such as... some really complicated things like executing code to get certain Pokemon from corrupted eggs. Or... well, battle with an egg if you have Pokemon in your party fainted because of this Pomeg Glitch.
Have you ever messed w/this glitch? I haven't, obviously, I don't quite understand it.