There once was a movie set staffer
Whose resumé no one sought after.
When he worked with the lights,
'Twas a horrible sight -
Shattered bulbs, broken glass - he's a gaffer.



I'm using the word gaffer to mean both the guy in charge of lights on a set, and also "one who gaffs", per the following definition:

gaffe also gaff, n:
1. A clumsy social error; a faux pas: “The excursion had in his eyes been a monstrous gaffe, a breach of sensibility and good taste” (Mary McCarthy).
2. A blatant mistake or misjudgment.
(dictionary.com)

So I took the liberty to create a secondary meaning of "gaffer", namely "one who makes blatant mistakes or misjudgments".