I've recently had to create a character and wanted to use SubSurface Scattering on it. But it also needed some transparency. Here's the Render Tree:
This particular character is also quite small and resides in the ocean, so it needed a little outline highlighting which was created using Incidence and Scalar2Color.
Here's the little fella:
Leafy Sea Dragons aren't really this transparent in real life, but it's a specific request by the client to fit in with their presentation.