The Ostwind or “East Wind” was a 20 ton anti aircraft gun built by Germany on an old panzer chassis. Production started very late in early 1945. Only 37 of the lanned gun were finised and only a handful ever made it into the field. The 37mm gun came with 1000 rounds and it could have brought down planes up to two miles in the air. But too little, too late. It has a 7.62mm gun on it, 100cm of armor and two barrels in a six sides fully traversable turret. They could not close the top of the turret becaue the 37 mm flak gun generated too much smoke.
Sources: http://www.tanksinworldwar2.com, bundesarchive, wiki