Many Pentax DSLRs are rated for operation down to -10 °C (14 °F). This is a selling point of these cameras, and they are specifically tested to operate reliably at this temperature (with a note on reduced battery life, recommending that the operator have extra batteries in an inside pocket).
I can't find any camera from Canon, Nikon, Sony, or Olympus rated to below 0 °C (to my surprise, neither the Canon EOS-1D X nor the Nikon D4 are rated to below 0 °C). Are there any other interchangeable-lens cameras designed to operate at below-freezing temperatures?