(Cross posting from the feature upvote site for further discussion)
While some waveforms would have extremely niche (if any) use, I think it could be helpful to have more options for curves than the current sinusoidal/cnoidal/perlin options. Sawtooth and triangle waves would both be extremely useful in a lot of scenarios, while square/pulse (along with half and quarter square/pulse) would definitely be extremely niche, but I can think of a couple uses.
Alternatively, giving the Curves filter node a curve output could serve the same purpose, allowing users to hand draw custom curves.