Spuhr or Badger uni-mounts with built in cant... Used various bases and rings for years, but these things just made a huge difference at longer ranges. Not knocking Geissele or ADM, which I know are superior mounts... just never used them... Yet.
Without a doubt... ADM Delta. Only mount approved by SOCOM for the SCAR. IMO, it's because it's the strongest and stops the rail flex during recoil from affecting the scope, lengthening scope life. Get the titanium lever version to save a couple ounces over the standard. Note: I don't think the 9.6oz weight is correct for both the Ti lever and bolt versions. I'm going to pull mine off, weight it, and subtract the weight of the scope and see.