I'm shooting something for school right now, and it has to be in the style of a director or type of movie. We're doing a humourous dialogue heavy scene, and it reminded us of Kevin Smith and Clerks, so we thought about taking it one step further and doing it in black and white just like Clerks. However, my understanding is that Clerks was black and white due to circumstance rather than artistic choice (ie. no money for more expensive colour film).
So other than "Kevin Smith did it in Clerks and that was our style of choice," I can't think of any reason to do it.
Looking through some older threads, I discovered that a lot of people have wanted to either shoot in black and white or convert their film to black and white. Why make that choice? Is it the content, for the visuals? Reading about it for still photography, some people think that certain things look better in black and white, like buildings or landscapes, because you focus more on the shapes. Is there a good reason to do it for people? For comedy?