M.Zuiko ED 300mm F4.0 IS PRO
This is the first lens I tested with the OM-D E-M1x at the Florida Birding & Photo Fest with an attached MC-20 (2x) teleconverter. It was amazing how easy it was to handhold due to the light weight; I was very impressed with the close focus distance, and the accuracy of the autofocus. This is an incredible prime lens for wildlife photography. I have used this in sandy conditions on Galapagos beaches, in rain in Florida, snow and -14 degrees in Yellowstone, and extreme heat in the Big Bend National Park area with no issues in any situation. The results with this lens by itself, with the MC-14 (1.4), and MC-20 (2.0) teleconverters have all been very impressive.