I enjoy that moment when you say a word aloud that seems perfectly normal, and someone mentions or questions it and you realise that you've never actually said it aloud before. Sure you may write, read, and think it--but it's never actually passed your lips. That's just neat.
Two words I like that are not oft-used would be Apropos and Convivial. I don't know as either is a favourite although I do love the former. Ubiquitous is nice too!
I just asked my coworker behind me about her favourite rarely used word, and she replied with Shenanigans. That may not be as rare as some, but it is lovely.
For me, obscure words lead into obscure looks. I prefer a heard-from, but not common word:
Spry has life in it yet, that's for sure.
I know what you mean about the looks, but for me at least the usage of seemingly obscure words is accidental. I think a lot of people have a larger vocabulary than they realise though, so it's not so bad and good to try and keep words alive.
/səˈpɜrlətɪv, sʊ-/ Show Spelled Pronunciation [suh-pur-luh-tiv, soo-] Show IPA
1. of the highest kind, quality, or order; surpassing all else or others; supreme; extreme: superlative wisdom.