Rhum is a mini-beverage found in the Pirates of the Caribbean fandom. It makes one talk like Captain Jack Sparrow for a brief period of time. It featured rather heavily in the second PPC Playscripte (and it has been observed that trying to talk like Jack Sparrow when not actually having imbibed any rhum is very, very difficult).
It is visually and presumably tastes the same as or extremely similar to common, garden-variety rum. Aside from making the imbiber talk like Captain Jack Sparrow, it does not carry the usual side effects of an alcoholic drink, such as a hangover. However, as it is alcoholic, it reacts violently with Bleep products and probably should not be mixed with any Stuffs, either.