I got a keychain that uses the radioactive decay of Tritium (the radioactive isotope of hydrogen) to emit light. : r/mildlyinteresting
Titanium Alloy Tritium Gas Lamp Keychain
TEC Accessories Isotope PRE (Picatinny Rail Edition) Glow in The Dark Keychain, Titanium Housing for 2 Glass Tritium Vial (Not Included) - Tritium Keychain Fob, Edc Key Accessories, Cool Keychain at Amazon