An interesting discussion went on in #suggestions about adding neutrinos to The Powder Toy.
The most notable thing about neutrinos is probably how non-interactive they are. (Randall Munroe wrote a really good article about this) This seems to be in direct conflict with the principles that make a good Powder Toy element; namely, having interesting properties and reactions that make it either fun to play with or useful in technical builds (ideally both, but that's harder to do than it sounds)
Per my element design philosophy, I don't think there are any "bad ideas" for elements. My approach to implementing neutrinos would be to either 1. do away with non-interactivity and create fantasy neutrinos that have some cool and novel effect loosely inspired by reality, or 2. find a way to harness non-interactivity to give neutrinos a use that lets them do something no other element can do.
I don't plan on adding neutrinos to any of my current projects, but I still don't think the idea is unworkable. I'd like to hear some of your guys' ideas on what you could do with them!
I´d opt for a 2nd type and make the neutrinos easily countable with a neutrino detector. The detector should output the neutrino count as serialized data to adjecent FILT and reset the count when an adjecent conductor (PSCN) is sparked. If there is some neat way of generating neutrinos (with a settable life property), subframers will probably find plenty of unexpected applications for them.
There could be several uses for neutrinos in The Powder Toy, if applied as @Jerehmia mentioned. However I'll link this article, almost a decade old. https://www.businessinsider.com/why-you-should-care-about-neutrinos-2013-12
I would like to see them produced after a nuclear power plant melt down, in game obviously.