The 3DConnexion Spacepillot Pro, specifically. It takes 3DConnex's previous SpaceNavigator knob and adds just about everything else a CAD pro, Pixar artist or Second Life sex addict could ever need.
Since I am none of these things, the spec page whirs just above my head. But the inclusion of a mini LCD screen for checking mail and selecting workflow macros is pretty great, as is just about every programmable custom function you could imagine. Mike, a Canadian CAD wizard, knows more than I, and he has a comprehensive review here. It's $500. [3DConnexion via Oh Gizmo, Design Engineering Review]