Blackbelt
When I first watched my older brother play Final Fantasy 1, he named his Blackbelt NATE after me. I've had an affinity for the class ever since. In retrospect, the FF1 classes are obviously based on the AD&D offerings: Fighter, Thief, Blackbelt (Monk), Black Mage (Wizard), White Mage (Cleric), and Red Mage (Bard). However, because I wasn't really exposed to D&D at this point I had no idea.
Rather than some Orientalist Shaolin monk, I had always imagined the FF1 Blackbelt as some jacked dude who beat people up with skill and power rather than mystical abilities. Think Ryu from Streets. This is reflected in the mechanics; the Blackbelt has no special skills in FF1 except for dealing more damage than the other classes and relying on no equipment.
As opposed to the typical D&D Monk, this is my take on the the Blackbelt class:
Blackelt Abilities:
You may use nunchucks, staves and shuriken, but cannot make use of any armor. Hit Die progresses as Cleric, and attack bonus and save progress as Fighters. You require 1200xp to level up, this value doubles for each level thereafter.
Your AC score begins at 8 and decreases by 1 each level until it reaches 1. Your barehanded attacks initially deal d6-1 damage, but increase by +1 each level. When the added value would reach +4, replace it with an additional d6. Thus, a 6th level Blackbelt deals 2d6 damage rather than d6+4. Damage caps out at 3d6.
At 1st level, you are only surprised on a roll of 1-in-6. At 4th level, your barehanded attacks count as magic for the purpose of overcoming immunity, and you may sense the presence of nearby creatures without sight. This allows you to fight blind in melee combat. At 6th level, you may easily punch through doors and stones with single blows, or bend weapons with your bare hands.
You begin play with nothing but your fists.
Note on Nunchucks: d6 damage. You may reroll damage. If the result is lower you receive the rolled damage, if it is higher you deal the higher damage to your enemy.
So what about Fighter? Obviously Fighter can equip whatever he wants, but how else do I differentiate them? I give Fighters a stronger than usual cleaving ability. Rather than only being able to do so against HD1 creatures they can do so against any creature. In exchange they gain additional attacks slower than usual (Every even level they may do an additional sweep, rather than every level). Fighters remain better against groups of foes, have more versatility due to equipment, and can leverage magic armour and weapons.
The Blackbelt gets no sweeping blows, sucks at low levels, sucks at ranged combat, has less HP, but deals more damage to a single foe at high levels. Until level 6, though, the Fighter will mostly be the better option to roughly equal damage and higher AC.
The other advantage, of course, is that a Blackbelt requires no weapons to function at full capacity. This comes up fairly often in my games.
All in all, Fighters are the better class. This is reflected in their higher HP value. While Blackbelts basically fulfill the same party role, I think they're different enough to be worthwhile.