Nixie Tube Power Supply
A nixie tube power supply that I documented at hackaday.io. Efficiency ranges from around 65% for 3.7V in, up to around 80% for 5V and 12V.
Here it is driving a bunch of IN-12 tubes at 177V from a little LiPo battery:
Here is a chart showing the maximum output current for a given input and output voltage:
PCB is on OSHPark. KiCAD and LTSpice projects are on my github. A full BOM with digikey part numbers is on hackaday.io.