I love the way the general flow of combat feels, aswell as the animations for attacks are really flashy and cool, things like ley lines, giant summons, samurai sheathe attacks, flashy mudra spells etc.
I feel like with each new expansion we get more awesome looking abilities, i remember the first time seeing Bahamut and losing my mind over it, never expected the devs to make something that big & flashy.

Though i will say there are some animations that i really miss from pruned abilities, Power slash, Aero 3 and Dark arts come to mind.
Maybe on day we will get a feature that lets us "glamour" old animations on to our attacks, because it feels sad that some great ones like Dark arts are just lost forever.