The WaPo's Choose Your Candidate quiz
But all this test really shows is how you like someone's rhetoric. Many of the candidates agree on various issues (and on some pages, Ron Paul's statements, though anonymous, stick out like a sore thumb), so all you're choosing is the candidate who says it best. Since action matters more than words, it's not exactly a good way to pick a candidate. It's a way to pick the candidate who spouts your favorite spin.