I went to the self proclaimed 'worlds largest tank museum' today. It was pretty cool, especially the scale of some of the things there. I'd say the coolest thing I saw was the WW2 King Tiger tank:
It must have been over 12 ft tall and the gun on the front could apparently shoot through just about anything the allies could throw at it.
They also had a bunch of WW1 tanks which where interesting:
And Goliath remote control bombs: