My list is only gonna address gameplay really, as if I took personality into account I WOULD need to make two lists. I'm also not gonna take remakes and ports into account, because if I did everyone but Tellah (due to not being playable at the end) would be tied first place thanks to how useful everyone became :P

1. Kain. Pure damage, and the ability to avoid damage while doing said pure damage, makes him one of the cheapest characters in this game. His jump has saved my ass from many bosses that do big attacks on the entire party. And it's all free.

2. Cecil. More pure physical damage. Early on in the game he can one-shot most enemy groups. Once he loses that ability the white magic that replaces it seems a little disappointing, but I like that he can join in as a fairly effective healer if you equip him with the right stat-boosting equipment.

3. Rosa. She's the most powerful healer in the game and her attack damage is actually really good as well. Not much else to say; I can't find much wrong with how she plays.

4. Edward. In terms of character, Edward is my absolute favourite character in the game, and I like him even more in the sequel. But that's not what's deciding my list here. When Edward joins, he can hang in the back row casting a free sleep spell on the strongest enemy in any group you encounter simply by attacking it. This buys time to pick off all the weaker ones and minimizes damage to the party (and stops him auto-hiding.) Then it upgrades to a confuse weapon, which means the enemies now do half the work for you. The Mom Bomb fight is easy because right before it explodes, you tell Edward to hide, then have him step back in and heal anyone that didn't survive. During the siege on Fabul you don't really need him as Cecil and Yang do tons of damage anyway. So I'll say this: anyone who thinks Edward is the most useless character does not know how to play this game. The way to exploit his strategies and abilities should be really obvious.

5. Rydia. It annoys me how little HP this girl has, but she makes up for it in pure insane damage potential. I hardly ever cast any of her black magic, other than Stop, Bio and Osmose because her summons upstage pretty much everything else she can cast, especially once she gets Bahamut as for some reason it's got an insanely short charge time. Then there's Sylph as well, which I tend to spam against single enemies until Rosa's learned her best healing spells.

6. Palom. Okay, so now I've listed BOTH of the game's black mages and we're only half way down the list? What?! Yes, I actually think the black mages in FF4 are very useful, and for the short time you have him Palom is brutal. I never found him running out of MP because his were so plentiful, and then he could equip all those staffs that enabled him to cast free attack spells during random encounters. Awesome.

7. Yang. I would've ranked him even lower if it weren't for me learning to use him properly, and I do find him a bit of a difficult character to pick up. For a monk, he's a surprisingly complex character to use.

8. Porom. Rosa's just better with a bow than Porom is, and so Porom is more likely to be spending turns doing nothing, or missing, at all those times she doesn't need to heal.

9. Edge. Damn. As much as I love ninjas, this one doesn't really do a whole lot of anything. Phsycial damage? Cecil and Kain already outrank him. Special abilities? Rydia's are better. Throw? Yeah, and keeping items in stock to do good damage is a pain in the ass. I'd really rather not have had him in the final battle.

10. As much as I think Cid is one of the coolest people in this game, he doesn't really do much in battle. He has high HP, but can't wear any good armour to stop him losing it. He does good damage though, and doesn't stick around very long so I can't complain.

11. FuSoYa. He's put in the party as a temporary caster of all the spells you haven't quite finished learning but runs out of MP if you try to make use of them. And that regeneration ability he has is kind of useless.

12. Tellah. What can I say? He's put into the party as a crutch early on to help you fight stronger monsters, but when he rejoins at Mt. Ordeals the fact he has such low MP compared to how much you now need makes him quite annoying to have around. As a storytelling device to convey that he's getting less useful in his old age it's all right I guess, but it sucks when you're climbing the Tower of Zot and he's the only decent magic user in the party because Cecil still sucks at white magic. So similar reasons to FuSoYa, only even more so because while you don't really need FuSoYa anyway, you DO need Tellah, and when you need him most he's virtually useless >