Getting any one level-up type to level 40 gets you a special accessory:

Warrior - General Crest - +50 Def
Monk - Dragon Ring - +50 Pow
Magician - Rune Earrings - +50 Int
Sage - Code Bead - +50 Mag
Thief - Wishbone - +50 Agl
Random - Crystal Ring - +20 in all stats