The Southeast Asian dagger, the keris (also spelled "kriss," or "kris," and usually pronounced like "crease," with a tongue-roll of that "kr" sound) comes in two basic varieties: straight, or wavy. There is a lot of lore about these blades, the kinds of magic that arises from the shapes, the dapur; or the patterns hammer-welded into the metal, the pamor, and encyclopedias written about what they mean.
There are kerises for health, wealth, and to prevent your house from catching fire. Some for warriors, executioners, and those designed to enhance your faith, sex life, or to protect you from being eaten by tigers.
The combination of dapur and pamor make the various kinds of magic, and expert empus, master bladesmiths, can do some amazing things in the construction of the the black steel (which is usually made from soaking iron, nickel-laced blades in arsenic and citrus juice.)
The number of waves in a blade is easy enough to determine, and I've done this short vid to show you how to count them.