One of my favourite past time is to dismantle cameras and lenses that I consider useless. Sometimes this turns out to be a costly mistake, because at the time I considered them useless, but few years later, they magically become hot commodities. The reason I do this, is to savage parts that I think I might use later on. I have a large jar that contains hundreds and possibly thousands of small screws of all kinds. I never failed in finding a right screw for any kind of job when I need one. It's probably the most valuable parts from these unfortunately cameras/lenses.
Sometimes, I only disassemble the lenses half way, because they make great looking pen holders, tools holders and whatever that you want to put on. The picture below shows one of my lenses converted to a tools holder. Prime wins for this purpose, as zoom lenses have too many parts that are hard to take out and put back together. The relatively simple construction of prime lenses are much easier to work with.
Nothing is worthless, it seems.