In all my years of diving here in Florida from Pensacola to Key West, the most aggresive fish that I have ever encountered has to be Damsels.
No, they won't rip you to shreds, but they are the most territorially aggressive, swim out and bite you, scared of nothing fish I have ever seen. Don't know the name, but they are about 3-4" long, black front/white tail.
I have accidentaly come face to face, literally inches, with very large green morays that scared the poo out of me but never struck. I have had 1 barracuda out of maybe 10,000 that I have been under with that took a swipe at me.
But those freakin' damsels will take a shot at you every time. Pound for pound the most aggressive IMHO.