You can see a fan being used fairly effectively here.https://www.youtube.com/watch?v=y4zz8Okgk2k
This was the only round I saw it for though, so I'm not sure how well it worked later on.
I'm reminded of Lisa Simpson's tiger repellant rock. First you have to convince me that the robots in that match were actually capable of consistently hitting 3-pointers. Then I might be willing to believe that fan was capable of deflecting hard thrown pyramid shots.
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The difficult we do today; the impossible we do tomorrow. Miracles by appointment only.