Henna. Beautiful, fun, exotic... and best of all... Do-It-Yourself (with a little practice). Also, unlike tattoos, it's temporary. Henna generally lasts for 1-3 weeks. An ancient tradition, henna is believed to "bring love and good fortune, and to protect against evil."
"As far back as 1200 B.C. the ancient Egyptians were using henna on their nails and hair. Henna was also used to dye animal skins, textiles, and men's beards. Once the henna plant's cooling properties were discovered, painting the skin became a way for the desert people of India to cool down their body temperatures." -Earth Henna.
Check out some amazing examples below. Scroll all the way down for Henna HowTo.