It would be nice if say you are a Barbarian, right? Okay, you can go to the Master Warrior place or something like that and learn special skills for being a Barbarian. For example a "Whirlwind" attack. That when you do a certain combination of keys or you double click the skill you will perform this attack. Another example is "Deadly Earth" or something like that where you smash your sword/axe/hammer into the ground and it sends a powerful earthquake attack to the target. And if you are a Wizard there would be something like "Rapid MP recovery" which would recover your MP faster. If your a Priest maybe a special "Summoning" spell?