Metabones Speed Booster
See the previous announcement of the Metabones Speed Booster and the additional discussion.
Update: I now have an early sample of the Speed Booster (Sony NEX to Canon EF version, the only version currently available).
Particularly intriguing is the prospect of a personal favorite: the Canon 40mm f/2.8 STM. That lens is especially beautiful wide open. But there are many other lenses to try of course, and it’s possible to try a few Zeiss lenses as well (ZE version as well as ZF.2 with lens adapter), as well as my Olympus 50mm f/1.2, which in theory should become an f/0.9 lens with the SpeedDoubler.
B&H Photo has a Sony NEX-6 digital camera on the way to me, so I expect to do some first tests by this weekend.