I think the folks naming Kevin Jones, Chester Taylor, Cadillac Williams, Justin Fargas, etc. are completely missing the point here.
These are all NFL backs who've had a shot and never really cashed in. The odds of someone having an opportunity and blowing it but later becoming a superstud are pretty slim. For those of you looking for next year's fantasy/dynasty gold, that is NOT the place to look.
A few years ago I was looking at Frank Gore as the next big fantasy stud. He looked great when finally given the shot in limited action, and the next year absolutely blew up. Michael Turner was the next guy I targeted for the same reasons. The bottom line is that neither of these guys had a shot and failed. Look at Priest Holmes years before that -- again, a guy who was just stuck in a spot where he didn't have instant opportunity. Once he got that chance, he was unreal. The same for LJ when he was behind Priest...
Way I see it, folks in this thread seem to be looking in the wrong places.
One of my best guesses so far would be Hightower. Kid runs like a maniac (reminds me a lot of Barber in running style AND haircut), is behind an aging Edge and, with some experience, could potentially be a standout.
Who are the other hidden gems? I don't know. But I do know it's not Cadlliac or Justin Fargas.