We have 6 month old male that I swear just came in Extra Feisty. When he was 8 weeks old it became apparent he had a mighty little hunter in him because he would attack everything that moved...and most things that didn't move as well. People who took care of him while we were on vacation and knew cats well were telling us things like (in sympathetic tones) "That's one very *male* cat you have there."
Despite loads of loving care and persistent discouragement in the people attack department he was pouncing and scratching up legs and biting hands routinely. Honestly I don't think having him neutered at ten weeks made any noticable immediate difference in the aggressive play department but I do think it prevented it from escalating. I do think the constant presence of humans is what keeps his aggression in check.
Since then he has stopped attacking/scratching up legs but that took time and gradually stopped. The biting has persisted and I think thats both play behaviors and "don't know my own strength" love bites. Our kitty doesn't like to be held and frequently will bite when he's picked up. The solution of course is to not pick up an animal that doesn't like to be held (!) which I know is easier said and done.
When we decided to keep him we had these images in our minds of nice long cuddles and that clearly doesn't jive with our kitty's needs/wishes.
One more thing--I have noticed his aggression does ebb and flow. He'll be cruising along doing pretty well and suddenly will have a week or so where he's feistier than usual and then he settles down again. I've never figured that out except I guess he's entitled to be a little moody now and then just like everyone else in the house.