MD421 is a classic. It's my best choice for recording toms and bass amps. Works great also on guitar cabs and snares, if you're after a bit darker sound. Add another mic beneath your snare, and you'll get a fat sound with a crisp rattle.
MD421 is notorious for it's clip that is prone to open accidentally. Not sure if Sennheiser has actually redesigned the clip for MD421-II, but I've had zero problems with the clip on my new mic. The mic stays firmly in place.
The appearence of the mic is timeless. A friend of mine thought my brand new mic was actually vintage, in a good way.
The ONLY con I can think of is that the cas_/box of the mic is quite big. It's way bigger than it used to be with the older model. I sometimes travel with my recording gear, and then the box is just way too big to take with me, thus I must pack the mic in my bag without its box.