Not just any sort: Swash-plate steam engines! What's that? Go see! Scroll down and play the videos; the operating mechanism is fascinating and uncommon. Crazier than an elbow engine! Internal-combustion axial engines -- swash-plate and kin -- have done serious work in places like torpedoes.
More conventionally: the largest hit & miss engine I have yet seen, in one of the odder applications. And you've gotta love the starter!
6 months ago