I know it sounds crazy, but is it possible to get a brighter sound or more detail or clarity on a dynamic mic (SM58, for example!) by recording without the grill? Or is that dangerous? I was thinking of giving it a shot, but I only own one mic and I'm not quite prepared to risk its life in the name of experimentation.

You take the ball off the 58 and it basically becomes a 57. Slight polar response change, but not really much.  Try it and you'll see it even looks like one....in a way.  The grills are transparent enough that you aren't diminishing any high end really and the nature of a dynamic mic will make it not as "crispy"...bright, etc as a ribbon or condensor.  Same with the detail.  Get ya a cheapie condensor...something like a MXL, to see if that suits your needs.  Realize some of the cheapies will sound harsh and not brighter or clearer....if that makes sense.  So get one that seems to get some good reviews online.  Not necessarily the best suggestion, but the 990/991 pair of MXL mics should be on sale at your fave guitar center type store for around $50 for both mics together...  Basically both small condensors...though one looks larger and the other more like a pencil style condensor.

The grill isn't there to soften the highs - the electromechanical capsule does that - but rather to break up blasts of air that cause annoying plosives. A 57 has a windscreen, too, it's just smaller and not as effective, which is why the 58 is preferred for vocals. But if you wanted to close-mike a guitar cab, removing the 58's screen might work.

Sweet! The cage doesn't do the greatest of jobs with plosives… just got me a pop filter for that problem. But I'll give the mixing amp a try- never done that before!

As you can see, with the pop screen unscrewed off the 58, it looks pretty much like the 57.  The lower picture shows that their polar patterns are about identical.  In other words, you really aren't going to hear a huge difference, if at all.  Try another mic if you're looking for better clarity and high end.  Bit's right...the 58 is preferred for vocals for the slightly better wind screen, with the 57 for instruments.  Like I said, basically the same mic...and the windscreen really doesn't affect the sound.  However, that said, you can use your 58 for a hammer...so you might sell your hammer and get an inexpensive condensor !!  :-)
 
 

I can't post links, but I came across this:
 

http://shure.custhelp.com/app/answers/detail/a_id/1916/~/using-the-sm58-without-the-ball-grill

 

It depends on what you're recording?
 
If you're recording vocals, it's different from recording drums, which is different from recording a live performance? 
 
I record in my living room, so it's not an issue for me... But I know there are different environments? I'm pretty good at recording "me" with my treated walls, and my tasty Neuman U87AI through my pre's... But in a live environment? All of that is out the window...