There have been players with more raw speed than Rocket Ismail, but I have yet to see anyone come close to what his football field speed was.
I still remember one of the 1989 kickoff returns against Michigan. It looked like the coverage guy (I can't remember his name, but I do remember he was timed at a legit 4.4 in the 40) had the perfect angle on Rocket, and that it should have been an easy tackle, but Rocket just kicked it into a much higher gear, and blew past him. To blow past a legit 4.4 guy like that was nothing short of incredible.
You could see some of the Michigan players throwing down their helmets in disgust on the sidelines during that KO return.