Penicillin
water chlorination
I don’t mean to quibble, but the Colt 45 (I own two) evolved from the Walker Colt that evolved from the Sprinfield 1825 Colt, that evolved from the pepperbox with rotating barrels. It was an innovation, but not a new idea.
Penicillin was a discovery, but not a new idea. China existed as a concept before Marco Polo popularized it just as antibodies existed before they were discovered and standardized.
Water chlorination is a bit tougher, but I think I could, after some research, show it was an innovation but not a new original idea. I’m not diminishing the revolutionary importance of any of the three at all.