@replikvlt No one thing in particular. I just like a well stocked cupboard. Sugar, salt, diamond dust, tritium gas, some polonium-210, gallium.. just your based day to day needs.
I've used it in a few experiments, betavoltaics, spark gap induction, and long-term glow in the dark devices.
@freemo@qoto.org I expected to hear betavoltaics.