Aviation connectors, like what Profezzorn, Jbkuma, Slothfurnace (and myself) are using.
The more pins the better, so you can split up the power leads and reduce the amps going through the individual pins (5a per pin I think is max).
The Teensysaber instructions show how. There is even a great little 3d printed adaptor Profezzorn designed, and made available for free on thingiverse. It Works great. Even if you don't plan on building the teensysaber, there are lots of good instructions on how to make different blades. The normal luxeon adaptor is very clever, and makes it easy to sneak into movie theaters (yes I will be that guy).
The little cat/rj45 connector doesn't look robust enough.
Had to mention, I hope that TCSS goes with a similiar concept.