
Arca-Swiss P0. Perfect for the 5D mkII with battery grip and various video add-ons. The locking collar makes repositioning pretty quick, although not as quick as a pistol grip.
It also has a dedicated panning lock, so you can lock down the head, and release just the panning axis.
It does use a new quick release mount, which I'm not super thrilled about, but the mount itself is solid.