Recently I've been swapping my kit around a bit - offloading stuff I don't use and trying some new bits.
I had a Canon 50mm f/1.4 that wasn't getting used and did a direct swap for a Falcon 14mm f/2.8 manual focus lens. (Falcon is a re-branded Samyang)
The lens has no electronic connection to the camera so doesn't report aperture or even have focus confirm (unless you mount a special chip). I tried a focus-confirm chip, but it was a waste of time - live view on a tripod is the way to use this lens.
Anyway, from my initial test shots I'm very impressed with this lens (nice review here)
It seems very sharp indeed with very little chromatic aberation.
This shot was an HDR of 3 images to bring out foreground details whilst holding on to cloud detail.
Canon EOS 5D Mark II, f/8.0 @ 14 mm, ISO 100