Asbjorn Lonvig's words: Sure a Kawasaki Z1 is cool, but I prefer a Harley. Don't tell the Japanese.
Wikipedia's words: The Z1 Kawasaki was a motorcycle introduced in 1972 by Kawasaki Heavy Industries. It has been described as the world's first superbike, but that term is probably more accurately applied to the BSA Rocket 3. The Z1, along with Honda's CB750, introduced the four-cylinder, across the frame, disc-braked layout.
The Z1 Kawasaki was developed in strict secrecy under the project name "New York Steak". Some years previously, Kawasaki, already an established manufacturer of two-stroke motorcycles, decided to make a 750cc 4-cylinder 4-stroke sports motorcycle; they were beaten to the market place by the Honda CB750. Apparently, the bosses at Kawasaki were horrified and ordered their designers to come up with something overwhelmingly better. The subsequent design was a 903cc bike with styling details that took the motorcycling world by storm and set a benchmark against which all future motorcycles would be judged. This iconic motorcycle has a huge and dedicated worldwide following.