Possibly one of the best bargains ever is the Contax 135 f2.8. It is relatively lightweight and compact, very sharp wide open, lovely bokeh, has smooth focus action, got a cool built-in hood, and can be found near mint on Ebay. A criticism of this lens has been its somewhat long minimum focusing distance (5.5 ft.) but it doesn't hurt its bokeh performance IMO. It's a Sonnar design, which I believe is one of Zeiss' best.
Here it is on my K1 without the hood extended:
How my little town communicates. Shot out my car window @f2.8:
Notice how easy it can be to get smooth bokeh and separate subject from background. OJ and latte cup crop:
Extreme crop OJ:
Artificial plant in front of lamp, lamp is touching back of plant but is already blurred enough to help the plant stand out. Of course, the thin DOF makes it a challenge to get images in focus wide open:
Extreme crop: