Games with Good Combo Systems?

[Nitishajack]

So I'm currently designing my own RPG system and one thing I definitely want in it is the ability to chain powers and attacks together into combos on a player's turn. I'm unsure how to implement this though. I want it to be fairly simple to learn and keep track of, so that it doesn't bog combat down more than is necessary. Are there any systems out there that do this well? I know about Exalted but what else?