What are your favorite businesses or communities in Houston that are "lesser known" but regionally or globally significant?

I was inspired by this thread, where someone asked for help repairing an accordion, and then someone linked what is apparently a hugely influential and popular accordion shop I'd never heard of.

I also learned last week that Houston has the biggest Nigerian community in the US.

I also learned that the Hindu temple in Stafford is the largest in Texas and one of the largest in the US.

I think that there is a lot of this in Houston–very niche businesses or communities, and so I started looking for lists or threads that could give name a bunch of them but couldn't find them in one place.

So, along this vein, what do you think are the businesses or communities which are not broadly known in Houston but are regionally or globally popular in their niche?