Round “War Shield”
     Just like the wheel, there is no need to re-invent the shape and function of the round shield - it's universal for a reason.
The round "War Shield'' is extremely resistant to damage over time simply by having the grip rotated as your attack edge starts to wear down (It’s sad, really, a circle being an inanimate object doesn’t even know how genius it is!). 
The round shield is also an optimal design in so many ways: able to protect large parts of your core body with small movements, hide your attacks and counter-attacks, and generate fierce, subtle, close-range shield punches.
Ask anyone that has ever been knocked from their feet, or ko'd from a shield-punch - they will never again underestimate the offensive capability of the shield.
The idea of the round "War Shield" will endure not only for its usefulness in combat, but also for the ability to fit kick-ass paintings and symbols on it!