Anyone who paid attention to boxing in the 90's knows the name "Prince" Naseem Hamed. Love him or loathe him, everyone had an opinion. He was undoubtedly a brilliant showman, and many people - myself included - think he was one of the most exciting, promising boxers the sport has ever seen.
If you're not familiar with him, here's a video of one of his better fights, in his prime.
As you can see, his style is totally unorthodox:
He usually keeps his hands down below his waist.
He rarely blocks punches in the conventional manner; instead, he relies on his reflexes and uses head and upper body contortions to duck or lean away from incoming blows, forcing opponents to hit thin air when they swing.
He is a natural southpaw, but an ambidextrous puncher.
He is quite small (he fought at flyweight, bantamweight, and featherweight), and very fast, but also has enormous punching power; he was constantly described as hitting like a middleweight (or occasionally even heavyweight).
His punches are bizarre and awkward; almost always heavy, lunging blows; thrown from all over the place (sometimes even behind his back) and coming in at crazy angles most boxers would never even consider attempting.
He often does something no trainer would ever recommend: leads with an uppercut. He gets away with it most of the time because he's simply too fast to be caught (he was only knocked down about 6 times in 37 fights, and never knocked out).
He switches his stance frequently, from southpaw to orthodox to square, and is equally dangerous in every stance.
One of his weaknesses is the result of his defensive and offensive techniques: because he avoids punches by throwing his body in all directions, and because he throws punches from such awkward angles, he is very frequently off balance and on the verge of toppling over.
For more information, here is an excellent article examining his style. Some excerpts:
When his opponent fired back at him, Hamed would swing the dropped right hand around, leaning back at the waist, and look to take the opponent's head off with a southpaw lead hook. There's a tendency to get hung up on Hamed's uppercut and left straight, but the short counter right hook was where Hamed did much of his damage in the ring. It was the threat of this counter that turned forty-punch-a-round boxers into ten-punch-a-round boxers against Hamed...
The classic Hamed lead uppercut was on full display [against Robinson]. In amateur boxing, dipping the head below the belt line is illegal, in professional boxing it isn't... but then why would you bother? For Hamed it became a set up. Bringing his head low, Hamed would weave back and forth below his opponent's vision and come up to the side with a lead uppercut. The number of opponents Hamed hurt with this boggles the mind...
Hamed's corkscrew uppercut was combined with a hop to the right to line up his left shoulder with the opponent's centerline, shortening the path of the left straight which followed. [Sometimes] Hamed angled to land a short left hook, something he also did regularly...
Hamed's leaps across the floor could put him in trouble - as when he lazily and repeatedly leapt at Barrera - but sprinkled in through a solid boxing performance, they were lethal...
- Vice Fightland: How Prince Naseem Became the King of Boxing
Unfortunately, Hamed had a fairly short professional career, consisting of only 37 fights; the last two fights (including his only loss) were extremely disappointing, and he had clearly been in decline for several fights before then. Following his only loss, to Manuel Barrera in 2001 (he lost on points), he fought only once more; he never officially retired, but simply faded away. He had gotten complacent and lazy, and his career is typically seen as one of enormous potential that went unfulfilled.
Announcers in his fights (including one of his biggest fans, George Foreman, who called him "the greatest fighter since young Muhammad Ali") often said he was one of a kind, and called his style unprecedented. I wish we had seen more from him, but that ship has sailed, so I am hoping for the next best thing: an heir apparent.