Cleaning things out for a garage sale, came across a pair of Nintendo DS Lites. They had not been touched (or charged) in at least 5 years, probably 7. Pushed the switches just for grins and they both turned on, that's some Nokia 5160 kind of longevity.
Also, I found out I had a somewhat valuable copy of GBA Metroid Zero Mission, felt like finding $40 in an old jacket.