I designed and machined a piston and bore assembly that uses adiabatic compression of air to ignite flammable materials like cotton swabs or tinder in order to help start fires (not for arson though). Every part was machined by hand on the lathe and mill. 

The piston is designed with a screw-off cap that exposes a cavity for convenient storage. Another screw-off cap on the bore helps to ease cleaning
The piston design features two O-rings in order to create a good seal that allows adiabatic compression to occur.