And then, of course, there's Ornithopters. The first onscreen version of Dune cut them out, as with suspensors they weren't necessary and not within the special effects tech of the time to pull of without looking like toys. "Sky Captain and the World off Tomorrow" had some, I've only seen clips but it doesn't look like they were any more realistic-looking.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
"The Mayan symbol for "book" looks a lot like a triple hamburger, but I've never seen them claiming it as proof the Mayans had Big Macs." - KaiYeves
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort