Product that you'd love to make,
but probably would not make any money.
I'd like to make a better glass vaporizer for DMT. Would not sell. It's a fringe drug even within the small psychedelic part of society.
Pretty much any toy that isn't Iron Man, Darth Vader, or flavor of the month anime. I'm still going to do it once I get out from under selling toys though. Fuck the market and its stupidity.