Best experience is the one I have now, work team is pretty good, and while we have the usual minor niggles with the other teams that share the premises even the site-wide team is pretty good, and boss is the type where any team-wide problems are hers to deal with (addressed with the whole team altogether and/or inidividuals individually as required) and any team-wide victories/praise is everyone's.
Also equally up there was my business with sibling dearest, we work really well together.
The "worst" experience (because I wasn't affected by it as much as I apparently should have been as in rather than being really upset about it I was slightly confused and was like oh well more time to work on the smaller projects that had kind of been on maintenance mode as the big company had been a big project that had taken up a lot of time) was probably the one working for the big company in the city that seemed to have undergone a coup.
What's been your best and worst? :)

I've had many "best" team situations, far too many to count and even remember.
The worst was at a place that talked a big "team game" but allowed cliques to form (even encouraged it) and that meant it was, I'm fact, completely fractured, toxic and untenable as far as a place to work for me. I left.
That sounds like the correct ratio to have XD
My brain is struggling to comprehend a place that encourages cliques, like why would you do that.
I know, it was terrible and the issues started at the very top with no regard to dealing with th obvious and damaging cliques. At the first work event, my wife was pulled aside by two of the other wives and warned about it. When she told me I talked it away not believing it but sure enough, there it was. I wasn't there long, just under 12 months.
Yay for the forewarning and being able to escape quickly! O_O