What language do you find incredibly useful that no one else seems to care about? I am not looking for the language with the coolest features, but the language that makes you the most productive. I realize that a productive language that no one uses is a bit of an oxymoron.
My personal choice would probably be ruby without rails, but I am sure others can come up with some better answers.
Lisp, no doubt.
May be Smalltalk too. In Argentina no one is using these.
None if it still exists. I have no doubt that there are some arcane, almost-never-used languages out there, but if the language still exists it will be used both as intended and in twisted and contorted ways.
Curl, of course!
I am totally biased, since I have worked on the implementation, but it really is a very nice language. It is getting used in Japan and Korea, but hasn't really caught on much elsewhere.