The Bob Semple tank was designed in New Zealand as an emergency improvised armoured fighting vehicle. It used a tractor as a base, had machine-guns as its main armament and used corrugated iron as armour. Only four of these machines were produced before the project was cancelled, and the tanks made were disassembled and had their function as tractors restored.
However, what could possibly possess the New Zealand government to actually put these things to use, let alone allow them to see combat?