The Shure SM7 is a dynamic recording microphone designed for broadcast speech I believe, but is also great for singers, among other things. It is built like a tank, as most Shure microphones are and can take a bit of a beating, although I wouldn't recommend beating it at all!
I've been using the Shure SM7 for about four or five years, and it has become one of my favorite microphones for male vocals. It is like a supped up SM57
, with more girth and body in it's sound. This mic is extremely underrated, and to me it can sound as good or better on certain people's vocals than any mic I have used. I would compare the SM7 to the Electro Voice RE20, since they are both made for radio broadcast and for speech application and are both in the same price range. In terms of tracking male vocals, I think this is way better mic than the RE20 and is probably a better all around mic. However, I would choose the RE20 for strict broadcast and speech use. I also like using the SM7 as a kick drum mic and on a bass amp or electric guitar amp. The best part about the SM7 is that it will cost you only a fraction of some more expensive mics, but is as good as any I have used in certain situations. If you are a male vocalist and have a project studio, I would definitley at least give this mic a try to see if your voice is a fit because when it is you can really get some good results - specifically good on rock singers with a bit of a growl, or for a screamer. All in all this is a great mic that I love having in my mic cabinet.