Yeah, there's a lot actually, so abs is pretty common and so is pbt, but then you get stuff like pom, which is another plastic but often produces a poppy (ish) sound signature. Ceramic keycaps are heavy and have a deep thock to them. There are metal keycaps which are really pricey and sound imo a little pingy but still pretty cool. I'm sure there are others but those are the main ones I see accessable to the general public