Pot and Knob shafts, Ds and Flats
It does look like some potentiometers are offered with options of where the full CCW position is. But anything other than the standard (30deg right of up, or about 1:30) is a special order part, or at least I couldn't find any in stock anywhere.

Here's an example:
http://www.mouser.com/ds/2/414/p160-20748.pdf