The choice kick drum mic at Grimshaw Audio. Most kick drum mics are pre-EQ'd in some way, with a large peak in the kHz range. I find that makes all kick drums sound very similar, which isn't great when you need something that works with a wide range of genres. A jazz kick drum does not need to sound like a cannon, for example.
The X1D is essentially flat through the kHz range, and also deep into the bass - I've found signals as low as 16Hz coming from some kick drums.
The flat response means the kick sound is easily tailored to the genre, making this an ideal mic.