> Maybe most of the above are too mainstream for the list. While an interesting language may be obscure, an obscure language is not necessarily interesting. I

> Maybe most of the above are too mainstream for the list. While an interesting language may be obscure, an obscure language is not necessarily interesting. In many cases, being relatively well known is a benefit simply because it offers more exposure to new ideas. I have found languages such as Forth, Racket, and Smalltalk far more valuable primarily because they are sufficiently accessible to be practical learning tools.