Rankings are often a heated topic in mixed martial arts circles. They're so very subjective; your rankings likely look entirely different than mine, and the fan sitting next to you at the bar likely has a very different opinion on the subject.
Rankings are also useless. As we've recently seen in the UFC, rankings are a mythical creature that have zero effect on title shots or perceived standing in each weight class. If they had any weight at all, we wouldn't have seen Vitor Belfort face Jon Jones, we wouldn't see Jones defending his belt against Chael Sonnen, and Nick Diaz would need to win at least one fight before facing off with Georges St-Pierre.
But even though they're useless, rankings are also fun, and nothing is more fun (or useless) than pound-for-pound rankings.
With that in mind, here are my pound-for-pound MMA rankings for December 2012.