I would have to say shino is. He's only in like 8 episodes tops in the whole series of naruto/naruto shippuden. In even when he's in a episode, he never talks or do anything worth caring for. I was going to choji but at least he gets some air time every now and then.
OT: Shino is a badass....he's just so stealthy he escapes the panel time !!!
I'd have to say Kiba. He still has part I Naruto's personality, but has no excuse for it. Where it is his cockyness and hot headedness, Naruto's drive was companionship and friendship....attention from being alone. To make it worse....he has gone through no traumatic experience or anything to make him mature like Naruto has.
Kiba is pretty cool, bit his personality is practically a polar opposite to mine.