I've used bit shifting a lot when dealing with any sort of audio/video applications. Specifically, when muxing audio and video into a container (i.e. MPEG transport streams) you need to set up a bunch of bit flags that are packed very tightly and also need to frequently need to write data into non-byte boundaries. The result is a couple hundred lines of code of all pointer arithmetic and bit shifts to convert between verbose data structures and the format in question.