1.) Yuffie-witten's Conformer. It plain rules. You won't stat max without it.
2.) Cloud's Ultima Weapon and Kitten Sith's HP Shout ( ) Doing 9,999 damage every attack is simple with this.
3.) Cid's Venus Gospel and Nanaki's Limited Moon. Since MP is never a priority like HP, these go under the 'higher HP = more damage' weapons.
4.) Tifa's Premium Heart. Ugh. I guess if you use Deathblow alot it would help, but they must not've been thinking the day in development when they made this weapon.
5.) Vincent's Death Penalty. All the other useful weapons are powerful almost as soon as you get them. This is not. I don't have the time to kill 9,999 enemies, let alone 65,000. I don't care if it can kill Emmy or Ruby in one hit or whatever.
6.) The only reason Death Penalty isn't on this list is well...Aerith's Princess Guard. It's uselessness is self-explanatory. Although it would be perfect for Ruby weapon (as evidenced by the Ruby weapon video), but you'd have to code her into the party.