I've gone through too many to be able to remember a count, however One Punch Man (Season 1, and only Season 1), have to be one of my absolute favorites,
Yusuke Murata saw great potential in OPM as the poorly drawn and gag webcomic by ONE, so he decided to re-illustrate the webcomic into the highly successful manga and anime it is now.
ONE wasn't really a skilled artist at the time, he just did manga as a hobby,
perhaps he isn't that good to this day even after Mob Psycho 100 (which wouldn't have happened if he hadn't been approached by Murata),
so in a sense, ONE's passions and dreams have finally been realized after years of being highly conservative about his works.
When Studio MADHOUSE approached Murata (and ONE) to have OPM adapted into an anime,
it has been said that many of the people involved pulled a significant number of favors that in themselves were by no means insignificant,
which resulted into the amazing work of passion and animated piece -on an average budget- that the first season of OPM was, or with the release of the second season, still is.