The Sennheiser e845 is designed for the stage performer. You can move with the mic without the sound ducking making it a good choice for beatbox. The e845 has a hyper-cardioid pick-up pattern helping isolate sounds on stage although this is rarely a problem for beatboxers due to the sound levels involved. It is also available as the e845s with an on/off switch.
My initial impression of the e845 was that I liked it. It has the same bottom end response as the e825s and e835 but I liked beatboxing with it and it felt good in the hand. I was a little surprised that the audio sample didn't come out as clear as the e835 and this probably has more to do with my mic position than the mic itself.
I ended up buying an e845 for my own use and I combined this with an RCF310a active monitor. It sounds amazing.
A pretty good mic for boxing the beat representing exellent value for money.