What's your favorite uncommon ramen style, preparation, or flavor?

You can get miso, tonkatsu, shoyu, and shio everywhere, even at most U.S. ramen joints. What's a less common ramen type that you really like?

Years later, I continue to lust over two bowls of ramen. One was an anchovy tsukemen with curly noodles and chashu, served in place called Nagi located in Shinjuku. The broth was super rich without being pungent. I had this in 2013 and have not been able to find anything like it again in the states, much to my disappointment.

Another was a tomato-based ramen with chashu in Takayama, on ground-level right across the street from the railway station. I had long given up on finding tomatoes that taste like anything until I visited Takayama last year. I'd never heard of tomato ramen before, but it really worked.