Once upon a time, I was peeling a banana in a dim and very dry room, and I'm pretty sure I saw a spark, perhaps caused by the same phenomenon.
I'm gunnuh try crushing an aspirin (acetylsalicylic acid) and see what happens. (ETA: My headache pills that have aspirin, acetaminophen, and caffeine, along with whatever binders, did not produce any light that my camera detected. That's the only aspirin I have and I'm only willing to sacrifice one of them. Oh well!)
ETA2: Wasn't able to get it to work by peeling a banana, crushing the inside, or crushing the peel, but I don't doubt it happened. Bananas probably vary a great deal. Thanks for the fun diversion, I haven't done an experiment like this in years.
Yep, and I probably should have mentioned, this was one of those giant, GMO-esque bananas, and it had a very thick, perhaps 1 cm skin, the interior of which was kinda fuzzy, such that peeling it was reminiscent of pulling apart velcro.