And if you want the absolute best: ROG Crosshair VII Hero. It clearly has the most robust VRM setup for overclocking and a full set of features to go with it (trouble code readouts, on-board power switch, switch selectable redundant BIOS, etc., etc.)
To be sure, it's really only needed if you'll be attempting extreme over-clocks with sub-ambient cooling setups. But that's also true of most of the other premium boards with extreme VRM setups, except absent many of those other features that makes it make sense.