Nothing grabs people's attention like an enormous -- and fake -- tattoo. If you happen to work in a business-casual environment, the effect is even better. Just make sure to apply it somewhere where it will be seen, like your forearms or upper chest.
Pay attention to size and quality. To go for a big fool, find the gaudiest fake ink you can. If you have a specific image in mind, Web sites offer custom fake tattoos and fake tattoo printer paper to make your own. Some costume shops carry nylon tattoo "sleeves" you can slip on if you don't want to endure an entire day with the Hell's Angels emblem plastered on your jugular.