The ever-so-famous "If you get a Magikarp or any Pokemon with Splash to level 90 and up, and it still knows Splash, then the move will be very powerful".
There was also the "Press UP+A when the Pokeball is in midair, and then hold A+B just as it opens up, and it'll work like a Master Ball". Though then again, that worked for me in any game. Sometimes XD Same with the "Hold DOWN+A+B when the Pokeball opens up". I didn't catch the level 70 Dialga and Palkia in Platinum in Pokeballs out of luck, after all.