Federated States of America John Henry Class Flying Robot

The great country blues singer Leadbelly once sang "Hear John Henry's hammer ring, Lord, Lord" and truly the FAS John Henry Class Flying Robots live up to the folk legends power.

Armed with a cannon and rockets, they are a powerful foe, if a little counter-intuitively designed: these robots can't walk, they can only fly... So why the legs?

Personally I love them because they remind me of the robot in one of my favourite movies, The Iron Giant.