Probably the most unique AoA indicator I ever saw was in Nebraska on a
homebuilt. Don't know what the aircraft was...open cockpit, high wing,
looked like a bathtub with wings and engine in back....and out on the
left strut attached with a pivot point was a crescent shaped piece of
painted aluminum that had its narrow edge pointed forward. There was a
90deg bend at the very top of the crescent to catch the wind not unlike
some stall indicators. On the face of the crescent, visable to the
pilot, were painted segments that read, "Not Enough - Just Right - Too
Much".
I still laugh at the simplicity of it!