My favorite lens at the moment is my Pentax's 150/2.8. It's responsible for a lot of the tonally rich & smooth, spatially crisp (but not clinical) prints I mentioned earlier in this thread. I liked it when I used it with film too, but if anything it's even sweeter on the 645D. Another one I really like right now is the Topcon (Voigtländer) 58/1.4 on m43 cameras via a Metabones SpeedBooster. Impressively sharp at the point of focus (which on Panasonic's GX7 can be placed literally anywhere in the frame) even wide open.
-Dave-
I also like the 150mm 2.8. It's not a very sharp lens wide open but it has a nice look. This past weekend I have been getting silly with a few of my cameras and have noticed that the differences between how the files come in (besides absolute resolution and DOF) can be for the most part equalized by lightroom. For example here are 3 images from the GX7, 645D, and A7R with the white balance set to the same numeric value. The difference between how the sensor picks up the colours is different, especially on the skin tones. All in all the GX7 is the most fun to snap quick images with, the A7R has the best image quality to size ratio, and the 645D feels the most like a tuned tool out of the three. For example being able to use it with thick gloves on in winter is something the other two cameras simply can't do.
GX7 panasonic 20mm 1.7 pancake at f1.7:
645D with the 55mm 2.8 at f3.5:
A7R with the 35mm 2.8 (at f2.
:
Here are some 16x9 crops from the images white balanced to a colour checker passport for each camera, in addition there is a frame from a black magic pocket camera:
GX7:
645D:
A7R:
Blackmagic Pocket Camera with the 20mm 1.7 pancake at f 2.2:
And here are three taken in what I thought was better light on the 645D without any tweaks done to the colours of the original raw.