donte stallworth is the fastest, but i was pretty sure i saw his number listed as 4.3..... the problem is where you get those estimates. Oftentimes they are from workouts or training camp which is done with a much-less precise stopwatch You really need to go by combine stats, as those are scored in a more controlled environment.
i'll try to dig up the huge article on mis-interpreting 40-yard dash times, but it was a good read.... you really have to add some time to everything you read due to inaccuracy.
Stallworth was the fastest around 4.3, but Laverneus Coles & Bethel Johnson weren't far behind to my understanding. Dante Hall is fast, but he's by no means the fastest... Like Wes Welker, his small size makes him seem more elusive...