For a thermodynamics class I decided to see if I could make a working water turbine. This is just a little thing I threw together to fit a spare 1.25" diameter DC motor I had laying around. I printed all the parts, which took about 6 hours (mostly due to the .1mm thick run I did for the turbine blade) and assembled them as shown. Due to some warping some parts needed sanding in order to fit together. Once everything was assembled, I fused the parts together with a soldering iron and extra plastic filament. Then I fused a 3/4 " tube to the top and added a water hose attachment.
it ended up powering a LED, generating about 5 volts with a water hose turned on half way (and generating about 10 volts by blowing into it) so it isn't that impressive.