My workhorse microphones are my pair of Royer R121's and my pair of Earthworks SRO's. The Royers, especially, I would feel fairly comfortable tracking just about anything with, with the possible exception of close-miking drums. Between the two pair I have about anything I could ever want in terms of natural-sounding recording capabilities.
As for one-trick poines, I'd put most large-diaphragm condensers into that category. Most of them seem to have a fairly distinct character to them that works great on some sources and not so well on others. There are a few of the more neutral-sounding ones, like perhaps Audio Technica's 4050 or AKG's C414B/ULS, that I've worked with that I'd consider to be workhorses, but I don't own those particular microphones. Large-diaphragm condensers I find myself using on vocals and just about nothing else these days, although I'd be perfectly comfortable laying down a vocal track with an R121 and a good EQ.
At this point I'd consider my SM57's to fall more on the one-trick-pony side of things than I would the workhorse side, since pretty much all I use them for is close-miking drums. I haven't felt the desire to put one on a guitar amp since I picked up my Royers. And I do have a D112 and an ATM25 I use on kick and floor toms that I'd put on the one-trick-pony list as well.
-Duardo