I'd love to specify wave types or even more advanced stuff such as FM synthesis. With a little work, modules such as this one may enable a whole new category of innovative/strange browser apps.
CoffeeCollider is a coffeescript clone of SuperCollider, it has a lot of options for subtractive/additive/fm/granular synthesis and algorithmic sequencing/composition.
http://mohayonao.github.io/CoffeeCollider/