1st - eXtreme Script Editor
It would be more easier for new/old/in hurry hackers. But I just wish there's a special reader-like-thing that will scan you're script and will tell you if you've done some errors in either spelling (eg, for instance.., some confuse \ with the / )...
2nd - Shinyzer
I've been wanting to have a shiny script encounter with my hack. And it would be useful to hacker with new ideas of, eg, PKMN SHINIES! :D
3rd - Advance Trainer
P.E.T. is useful, however, it's still glitchy, for instance, I can't edit the PKMNs that twins or any trainer's which battles you in a double battle, and I can't edit the PKMNs of the Elite Four... And, in PET, the attacks aren't the same attacks to be used in the game, for instance, String Shot is another attack in the game. T_T It would be very useful if it'll be done. :)
4th - Pokémon Editor Advance
I am kinda annoyed editing the PKMNs POKEDEX entries using A-Text, and so, this would be very helpful, indeed.
5th - Strengther
Changing the weaknesses and resistance of any PKMN Types would be very helpful, indeed...
6th - Titlescreen Cry Changer
A helpful tool to those who choose to hack either FireRed/LeafGreen ROMs and has the desire to change the token POKEMON in the title screen.
and last, but not least...
7th - Advanced Item
A-Mart exist for that job, however, it will depend on how they differ from each other.