I second Ron's answer, with a caveat: don't include most of the pipe bands.
I've seen several dozen different clan and fashion tartans at Highland Games, with multiple tartans in evidence at clan tents (for those that have more than one tartan).
But I've lost track of the number of bands that wear the Royal Stewart. Yes, it's an "universal" tartan, but of the hundreds of tartans to choose, why does every fourth band pick that one? (Although it is entertaining to watch the massed bands become "mashed" bands when two or more bands show up in Royal Stewart kilts, matching diced hose, matching khaki shirts ... and then try marching )