Air-cooled rules! Water-cooled drools!
Subbies are the go-to, because you can get overhead cams in a boxer. The air-cooled contingent is embarrassed by the 72° V-twin Hardly-Ableson. Here's a Motoguzzi:
Chopstix: Not my tiny house; and I suspect it was a one-off, being made out of plywood as it appears.
Mine looked more like:
