Combat

Obviously combat is a key component of the vast majority of games, I cannot personally think of an RPG in particular that does not have combat.

So. Which type of combat do you prefer? What type of system do you like? Which games do you think of when you think of great combat systems?

More importantly how should combat be synthesized into an RPG? By this I mean what does it take for combat to help promote role playing? How should combat be utilized?