This writeup was inspired by the world's most flexible programming language. Basically, what fully-functional Turing machine equivalent language has the most specific application? Meaning that, even though the language is technically able to accomplish any programming task, it's best used for one purpose and would be terribly cumbersome and reasonably stupid to do anything else with it.

My vote is inform. Its only purpose is to create interactive fiction. Infocom forever!

Any others?