The sites I'm most interested in are the ones that were ranking #1-3 for several months before entering an extended yo-yo for all phrases except domain.com; I've seen 90 days on / 90 days off, 45 days off / 45 days on, etc. Some of these sites were strong enough to have sitelinks on generic phrases for a while, so that's saying something.
I haven't found one like that - it really is "saying something."
The most intense yo-yo situation I've seen was for an internationally recognized brand (you can probably sing their TV jingle) and it hit their flagship site. But the yo-yo only affected a keyword they hadn't intentionally pursued before and recently began intentional SEO on. Instead of the expected "pop to the top" they got a yo-yo for 90 days, and ended up ranking at the bottom end of the yo-yo, not the higher end.