Open Shading Language (from Sony) uses it to parse the, umm, shading language.

Pixie (the Renderman renderer) uses two or three bison grammars.

I personally like SQLite's lemon parser generator for my grammar poking arounding when I'm not messing with my C++ Earley parser implementation -- which I can never seem to get working properly with empty rules since the papers on the subject are less than clear.

But I'm probably a bit of a strange one in that I'll spend days getting a random grammar working then drop it for some shiny new thing to play with.