Every year in July or August in Kandy, the ancient Sinahese capital of Sri Lanka, the Buddha's tooth is taken from the Temple of the Tooth in the center of town on parade around the city. It's by far the most amazing thing I saw in my year in Sri Lanka, with hundreds of elephants dressed in sparkling costumes, surrounded by fire dancers, musicians, etc.
Warning - this event is very popular and security is tight. I was there before the end of the war, so it may be more relaxed, but we had to go through metal detectors and pat downs. Plan to arrive the day before, and try to stay in a hotel along the parade route. This will help you to get a good viewing spot. Otherwise, the route gets two crowded and you can't see anything. There are a few backpacker spots along the route where you can pay extra in advance for a table or chair on the balcony overlooking the parade. Make sure you've eaten and gone to the bathroom before the thing starts, as it is several hours long and if you've gotten a good viewing spot, you won't want to leave it!