Daryll Clark will never be underappreciated by moi. Kerry Collins was the best ever. DC is my all-time favorite and will always remain so, with apologies to tremendous guys like MRob, McS, McG and a host of others.
Another guy who is always under appreciated is Tony Sacca. He was just a little before his time. Big guy who ran like a deer and a cannon arm. Put him in today's offense and he's All-American.
@leinbacker mentioned Evan 'Rolls' Royster. Combined a little speed and a little power, nothing really spectacular, but THREE 1,000 yard seasons and IIRC when he graduated, he was our all-time leading rusher, More yards than Franco, Cappy, Lydell, Enis, Warner, Carter, any of those cats who were undeniably great. More rushing than any of them. Also a really good pass-catching back.
They don't call it Generations of Greatness for nothing.