Quick Take: Sennheiser MKE 400 Mini Shotgun Microphone.
Here is a quick take on the Sennheiser MKE 400 mini shotgun microphone. It is a great tool for HDSLR work. We beat the crap out of ours and it always performs. The only downside is no real indication of battery life. There is a small blip when it is turned on but then it goes away. We have to turn it on and off throughout the day to make sure the battery is still good. It is one of the smaller on-camera microphones on the market for HDSLR work. I highly recommend using some kind of separate sound recording device like the Zoom H4 when sound is critical. However, this little shotgun mic will work well in a pinch. The Sennheiser MKE 400 retails for just under $200 US.