Two of the red-filter 2AA maglites, one on a headband, the other on a lanyard, for in the cockpit.
A bigger maglite for the outside checks before flight.
One of those little LED jobs to hold in the mouth when all else fails. Belt and braces and backup!
I usually spend about 15 minutes inside the cockpit setting things up before I start taxying at night. That gives my eyes time to adjust, and give me time to set up the nav and comms frequencies I'm expecting to need.