The first two are #cats of cohost and #dogs of cohost.
Then there's #The Cohost Global Feed. I sincerely love the fact that it's a tag. You can opt into looking at it and you can opt into posting to it, because it's just a tag. (I don't even know whether this was created by the staff or something users just came up with and adopted on their own.)
[Edit: Thanks to tips from the comments, I found the genesis of #The Cohost Global Feed!]
Lastly, I appreciate #coho film club, where analog photographers show off their art.
What are y'all's favorite tags?