Environmental Graffiti has a great list of crazy tools inmates used in their escape attempts. My personal favorite is the shotgun above.
This was more than just ingenious; it worked as well! A shotgun made of iron bedposts. The charge came from lead in curtain tape and was set off by AA batteries. Prisoners took a hostage, fired at a pane of glass and broke out into a waiting car on May 21, 1984.
They're all fascinating though.