HIckenlooper is the interesting one to me. If he's been vetted, it's been pretty damn far under the radar. He's a safe, white male. Not going to riffle too many feathers. He doesn't have Kaine's issues. (The money/gift thing.) I don't think he's uber exciting, but I at least like the idea of him more than Kaine.
He came around on weed in CO, as I recall, so he would prevent the crucial Sanders -> Johnson hemorrhaging!