post your favorite Glitches+ Secrets here.
I discovered a glitch in Diamond, where if you use Blisseys Softboiled outside of battle, you can raise a pokemons HP over it's limit. Here's how it works: at the top of your party have a pokemon with less then full HP. The pokemon below it must have full health. Chose Blissey's Softboiled, place it on the top one and press a+↓ simultaneously. The game should be tricked into thinking softboiled was used on a pokemon without full health, and will cause their HP to exceed the limit, i.e. Drifblim with 764/369 HP. Not sure if it works in other games though.

Screenie?

My favorite glitches are in the Red/Blue games. You don't need to know the names to know what I'm talking about.

            There, screenshots from Platinum. Next i'll see if it works on B/W