I used TukUI for a whie because Elv UI was to popular and felt tukz needed some love. Then I developed and used
BobUI (of which I swear I'm the only one that uses it I literally never met anyone else that active uses BobUI /sadface) which started as a collection of addons, but eventually grew into it's own thing. Nowadays i no longer play however I do maintain my addons and even BobUI (which is going through a 7.0 rewrite)