Lucky the Leprechaun has a green hat with a four-leaf-clover in it, and loves it so much, he once replaced the clover marshmallows in his cereal with two-color marshmallows shaped like it.
Cap'n Crunch not only has a Nice Hat (with a "C" on the front, in case you forget his name) but it has been known to double as a weapon sometimes, usually when the Soggies are his enemies. In one commercial, it conceals a miniature Gatling gun (which uses his cereal as ammunition, naturally) and in another, he folds it into a working boomerang.
The Minder entry in Live Action TV mentions Arthur Daley's trilby. At the same time that the series was airing, Arthur's actor, George Cole, was making a series of adverts about a remarkably similar dodgy businessman "laughing all the way to the Leeds" as he took the proceeds of his dodgy dealings to his favourite building society. The only way viewers had to tell that this wasn't actually Arthur was that he wore a flat cap instead of the trilby.