Myself I am a fan of the NiMH rechargeables in AA and AAA format. My dental hygienist wanted me to get an electric toothbrush, I found the bottom-of-the-line model that takes AA batteries for about $15 less than a model with an integrated battery which is totally easy to use with NiMH batteries.

I also had some old FRS radios

https://en.wikipedia.org/wiki/Family_Radio_Service

that I took out of mothballs. These had proprietary battery packs that can be replaced with AA's or AAA's, I found the old battery packs had gone bad but breathed new life in them with NiMH batteries.