The Aztec empire had some fascinating and beautiful aspects, from their temples to some of their traditions. One of the most intriguing albeit terrifying little things to come out of this ancient tribe has to be their Aztec Death Whistle. It's shaped suspiciously similar to a baby skull, though it's probably just made of carved ivory or some other precious stone (I hope). Used while marching to war, the whistle sounds like a mix of a banshee screaming and a 100 humans dying, and it apparently used to be made with actual skulls originally.
Watch this video of the whistle posted by Mileán Ó Raghallaigh below! Skip to 0:50 for the noise.