ShakeIt is a grammar mutation engine targeting browsers and PDF readers. For a given input, such as a web page or PDF file, and an output location, it will generate N mutated test cases. It was implemented in C#, but can be ported to other languages and is meant to fit within an existing fuzzing framework.
You can download it from the following link: https://packetstormsecurity.com/files/download/134562/ShakeIt.zip
Source: https://packetstormsecurity.com/files/134562/ShakeIt-Grammar-Mutation-Engine-Fuzzer.html