Just to turn things around a bit (like above), the discussion "what lenses do you prefer?" could instead start something like "what do you prefer to photograph?", and then leading over to lens choice.
"I hate zooms", for example, is pretty well-heard when discussing lenses. Sure, I do too, most of the time, but not at those instances when I'm in an airplane; up there it's the perfect horse. It takes too much time to change a composition using the radio to move an airplane closer or farther away, so a zoom is much needed, and the bigger depth of field is not a problem compared to fixed lenses, since the surroundings are normally calm anyway.
On the other hand, when trying to reduce a cluttered room to get some attention on the person occupying that mess, f/2.8 just don't work that well for me; f/1.2 or f/1.4 is more like it. Or when trying to balance low ambient with flash, and wanting to get as much ambient into that exposure without using a tripod, f/1.2 is a lot better than 2.8. Such a problem solver. I'd hate going back to medium format...
Further, when doing architecture, one or two shift lenses is always good tools; to make converging lines parallel, to remove the reflection of the camera from a reflective surface, or to stitch images together to get to that huge resolution a panorama might need.
So let's start with some general courses; these are the Canon ponies I normally bring:
People:
35/1.4
50/2.5 macro
85/1.2
Architecture, landscape:
14/2.8
24/3.5 tilt/shift
35/1.4
50/2.5 macro
90/2.8 tilt/shift
Objects:
24/3.5 tilt/shift
35/1.4
50/2.5 macro
85/1.2
90/2.8 tilt/shift
180/3.5 macro
Aviation; in air:
28-70/2.8
70-200/2.8
Since I've grown very depending on my 35/1.4 and 85/1.2, I'd also love to have the 50/1.2, but the two examples I've bought have both had the well-documented issues described everywhere on the web; a focus error that can only be calibrated for at one specific distance. It seems to be built into the optical design; there's no way to get it to focus correctly at *both* the near limit and infinity. My conclusion is that people saying that this is possible are probably not critical enough to see it.
Interestingly, I've owned a 80/2.0 Carl Zeiss medium format lens (for the Contax 645) back in time, which seemed to share the same problems, also being a very bright normal lens.
The above horses are all good for their respective courses. But do skip the cute little fat 50/1.2 ponie, unless your course is always of the very same exact distance...
