Rand Paul is the only Republican I'd have to seriously consider voting for, because with the exception of Ron Wyden, he's the only politician out there who talks about privacy and civil liberties even when it's not advantageous to do so. I mean, his presidency would likely fuck over a lot of my friends, so I'd probably vote against him and be bitter about voting against the only presidential candidate I'm ever likely to see come down on the right side of an issue I'm personally invested in for the next 8 years, but I'd consider it. Fortunately (?) he doesn't have a chance.
He's also the only one that talks about the dangers of going all "Rah! Rah! America! Fuck yeah!" In regard to foreign policy and implores people to consider the consequences of our actions.