If by classes you mean weapons then
Tachi - Class name Vanguard - Abilities, Mix of Ninjitsu Magic, Samurai TP Abilities, and some of the missing Dragoon and Monk skills with a bit of Mystic Knight/Sword Magic mixed in.
Warscyth - Class name Corrupter - All the oldschool Dark Knight abilities like Soul Eater, Bio, Etc. as well as new melee abilities.
Great Sword - Class name Soldier - all the oldschool Knight Abiltilities like Helm Break, Armor Break, Weapon Break, Shield Break, Etc.
Sling Shot - Class Name Mimic - A Mix of all the old school Mimic, Blue Magic, and Geomancer Skills.
Crossbows and Rifles (Not Handguns) - Class name Sniper - Learns more Ranged Attack abilities that deal with using elemental damage with the weapon and dealing damage from a further distance then Archer.
Hammer (Two handed) - Class name Sipahi - Does massive blunt damage skills and inflicts various status effects with attacks, also has some healing skills that are powered by TP.