alethiology - the doctrine of truth; that part of logic which treats of truth

Pullman, in the His Dark Materials trilogy, introduces an 'alethiometer', a truth detector. I recommend the books highly (though sadly they may not be available in the US) - even over Harry Potter. (Yes, they are, notionally, for younger readers..... yah, boo, sucks!)

cheer

the sunshine warrior

The only obscure word I know (and it's obscure only because most dictionaries don't have it) is Robinsonade.