Sennheiser E 901

I choose this primarily for the convenience of being able to throw something inside a kick drum and to not having to worry about setting up a mic stand. Reviews on its sound quality seem to favour this over similar offerings from Shure and Beyer Dynamic.
It's heavy - I assume to prevent it moving around, which it doesn't - and it sounds good on a kick drum and doesn't distort.
It uses an electret capsule, tuned for high intensity sources so trying to record anything quiet with this (e.g. voices when it is on a desktop) will result in unwanted hiss.
Beware using this as a jobbing live sound engineer, the holes in the front skins of some kick drums are too small for it to be passed through.