uh, you do know that selphie's The End... limit break deals exactly 0 damage - it inflicts Death status with 100% probability and ignores Status Defense. But Zombie-Status ALWAYS negates Death, even when it ignores Stat Def, so it'll never work on Zombies.
@Ultima Shadow:
1. Look at the vid i posted. He's got 255 Luck, and STILL doesn't do 9999 damage each hit.
2./3. Oh darn, I'm SO stupid! I play the german version of the game - whenever I said AP, i actually meant quick^^
3. Is AP the ammo you can get by converting Tonberry Knifes? If so, it actually ignores the Def stat (Pulse Ammo does as well).