For my main camera, the 5D MkII, the only lenses I own are the 24L MkII, the Zeiss 2/50 Makro-planar, and the 135L. I used to have many more lenses, both zoom and prime. Occasionally I'll rent something else, but for the most part, these 3 lenses are all I need. Frequently, I won't even carry all three with me when I'm out doing something. I've found that instead of limiting my photos, it's actually made my photos better, as now it's easier to visualize the shot in my head before ever even raising the camera to my eye.
I shoot mostly landscapes and events. Landscapes are easy with prime lenses, just move to where you need to be. Events are easy too, since the fast apertures are very nice, even with flash (which I always use at events), since fast lenses can get photos where the flash effect is subtle.
The makro-planar is only a half-size macro lens, but that's fine with me because I do not shoot macro photos. I use the lens because of it's great sharpness, flat focal plane, and lack of distortion, all of which are great for landscape photos. I also shoot the occasional product photo -- and the macro lens is great for this too.
I could ramble on all day, but this basically just boils down to my shooting style, and what works for me personally, like has already been said.
The nice thing I've discovered with Canon's prime lens lineup, though, is that there are no bad eggs.
