The highest profile one is /r/piracy. The illegal sharing part of the subreddit spawned a forum for good general piracy discussion. It was at serious risk of being deleted and had to go to extreme lengths to preserve the community that formed around the actual illegal sharing part.
https://www.vice.com/en_us/article/qvygwq/reddits-piracy-sub...
/r/datahoarders and /r/opendirectories are a couple other I personally have seen similar things happen. In my opinion they're a couple of the greatest subreddits out there so the fact that they could be banned out of nowhere on a technicality is a little concerning.
