As a kid, I thought the whirlybird turbine vents were cool. Growing up northwest rural MO we had a lot of high winds and some tornadoes, so I imagine quite a few of those had to have been ripped off from its base due to strong prevailing winds. Nevertheless they were quite popular.
I also thought that the directional rotating chimney caps were cool, the kind that looked like a robin.
As for other vents, I always wondered about the huge grates/grilles/shutters up high on the exterior wall or gables of commercial/industrial buildings. That usually meant there was a huge fan behind it, which of course I was very interested in as a child. I always had a fashlight with me and would try really hard to shine some light through the slats (which were 20+ feet high) whenever the stars aligned and I was near such a building and it was getting dark out (e.g., family night at my grade school which had huge gable slats--definitely a big belt driven fan behind it, or an evening trip to the Hy-vee store, where I would beg my parents to let me try to see what was behind the big grilles high up on the exterior wall behind the store and other stores in the shopping center). We also had a Modine and Nestle plant in town so whenever my parents would drive by it, I'd tell them to slow down so I could see all the different fans and machinery attached to the buildings.
However, even though I was interested in fans, I was kind of spooked about the big industrial ones or any exhaust fan with metal blades, even if it was a small bathroom exhaust fan (weird, I know). I liked them all, I just didn't want to be standing directly under one or near one in the dark. Now as an HVACR tech, I could care less, and I've been near huge ones taller than myself, in the dark, running full speed, some of them a not too far from over my head
