Tanks are a love of mine and I enjoy showing others the joy of these glorious machines. My submission is the glorious KV-2, a monster of a machine with a 152mm cannon shooting a 40kg projectile.
And as you can see, People loved climbing on it
The only thing better than the photos and the actual work done by the builders are the comments at the end of this exposé!
http://www.zerohedge.com/news/2014-09-29/presenting-isis-beating-mad-max-battle-tanks-and-buses