Radboy

Just in case you were worried about gamma rays and only had a GameBoy handy.

Robopon had an infrared photodiode
Kirby Tilt'n'Tumble had a gyroscope
Boktai had an UV sensor

Radboy has an SBM20 !

How it works

4kB EPROM
EPM3032 CPLD
MPSA44 transistor
SBM20 GM tube