The hat during opening titles
There's a great shot of the hat sitting on leaves, perfectly centered in the frame with the title of the movie above.... Then it blows away... How'd they achieve this? Its easy to say they used a big fan, but none of the leaves are blowing.
You could also guess that they pulled it on a string, but it keeps blowing away into the distance with no person pulling a string in sight.
I'd have tended to have believed it was CGI, however this film preceedes CGI.