Picture of Woot Light Costume Hat
Though this is labeled as a "Woot-Light" hat, a quick change of colored materials can net you just about any other "Lighted" hat. Drop the name and add your favorite hockey team to the foam and you have a hockey goal hat. Switch the yellow out for some blue or red and you have a police light hat. All but the resistors and LED bulb were found parts around the house. Total cost was about $8.00 for the resistors and LED bulb.

Parts List:
One Gallon Ice Cream Bucket (scrape the logo off of the side with a razor blade)
One spare male USB cable - cut from some cheap USB device that broke
One Bic Stic Pen
One large click pen - The barrel must fit over the Bic Stic pen's barrel
One spare computer fan motor (I think that is where I scavenged it)
Probably 30 inches of wire
One 25,000 mcd white 3.5 - 4volt LED bulb
One 220 Ohm resistor
One 50 Ohm resistor
Two Dixie cups
about one square sheet of aluminum foil
One heavy duty rubber band
Choice of colored film
15" x 17" of foam
5 volt USB charger (or simply plug into your USB port on a computer)
Electrical tape

Tools list:
Solder iron
Voltage meter
Hot glue gun