Hats can be lots of fun during a presentation and they can also help you keep on track without using notes.
I use hats as an outline of my presentation. Let's say I was talking to a company about the past, present and future of their marketing. I might use one of those funny ball caps that has a long pony tail attached to it and talk about how when this company first started it was wild and carefree in it's marketing efforts.
I would put this funny cap on or have an audience member volunteer wear it. The humor really starts here and in many cases you don't have to say a word. The audience members may start picking on one of their male buddies who is bald or one of their short haired female colleagues who always wanted long hair.
Next I might use a top hat to signify a more conservative old time banker when I talk about the growth years of the company up until the present. Again, I wear the hat or pass it out to an audience member.
When I talk about the future, I would use some kind of spaceman, futuristic looking hat that maybe had antennae attached. Some of the magic shops carry a funny lie detector hat with wires all over it that you can operate by remote control. You could make up a funny lie detector test customized to the company and have a participant on stage who lies about every answer. I've seen that an it is hilarious. If you can get the CEO up there with the hat on (make sure you clear it with him/her in advance) you will most likely hit a big home run.
You might be good at folding newspaper into hats which would be fun. You could pick one of the characters in the crowd and fold up a hat using the "Wall Street Journal" and say, "this is as close as the information in the WSJ ever gets to Joe's head.
"You can also get a chapeaugraphy hat http://www.chap-o.com which is a brimless piece of felt that can be twisted into many funny hats.