(Even though I think the thread starter is not looking to far back for his answers, a lot of you don't understand what he's asking. He's not saying who was the first person to do things, he's asking who made it a trend.)
With that said:
Big Boi - Throwbacks (young kids think it was Fab, but Big Boi really was doing it way before fab)
Prodigy - long chains (before P, everybody's chain came down to their chest)
Jim/Juelz - tight jeans/ rockstar look
Jay-Z - button ups, maybachs, rapper/CEO, "I'm not a rapper, I'm a hustler"
Puff - Mohawks