You guys left out only the greatest design ever. The Wankel Rotary Engine. Capable of high rpms over a very sustained amount of time, and the power they output for the size makes everyone want to handicap them just to save face. Only 3 moving parts and the ability to run at 10-15K rpm all day long for hours on end.
Plus its like legos, once you learn how to build one you can just keep adding rotors and the horsepower increase is susbstancial.
Our simple little 1.3L rotary puts out over 220HP. The new 1.6L is supposed to put out over 300HP.