What's a language that is really unpopular but you quite like. For me, it's J. Some of the idioms in J are a little annoying at first and the learning curve is pretty steep, but once you can read it quickly, you can see the whole program at once.
I like Piet. Some of the idioms in Piet are a little annoying at first and the learning curve is pretty shallow, and once you can read it quickly, you can see the whole program at once.
I like bonercoe. Some of the idioms in bonercode are a little annoying at first and the learning curve is pretty shallow, and once you can read it quickly, you can see the whole program at once.
I love J/APL for mathematical stuff, but I've never really written an entire program in it. If someone decides to make another /prog/ challenge, I'll do it in J, though.
Befunge is great to write in. I like GolfScript, too; it combines stack-based programming with functional programming features (map, filter, etc.) making most programs take a really short time to write.