Weslye Saunders could have gone pro after the 2009 season. He was well regarded around the conference as a tight end, and he probably would have been selected in the middle rounds of the draft. He decided to come back for his senior year to improve his draft stock, but it's been all downhill since then.
According to this report, Saunders failed to file some paperwork required for entry into the 2011 NFL Draft. It was extra paperwork that's required because he didn't play at all for South Carolina last fall. As a result, he won't be available for selection on draft day and has to hope someone will pick him up in the supplemental draft.
Saunders was part of two of the bigger off season scandals between Marvin Austin's South Beach Party and the Whitney Hotel. He also lied to his coaches about missing a team meeting, which is never a smart move. It's doubly so given that his excuse was that he was being interviewed by NCAA investigators over the Austin affair, something that the compliance department could easily refute.
Saunders could have contended for first round status with a good senior year. Instead, he's labeled as a big character risk and will have a very short leash with any pro team he might find work with. That's perhaps as strong a cautionary tale as you can find.