Borrowing from the idea of the Pluspora Check-in get some tabletop conversation going. If you have any questions that you want to get on the list to be asked, let me know. Also, if you'd like to be added or taken off the list of participants, let me know.
Which tabletop gaming item do you wish you had never given away?
I had to move in a short period of time, and had to leave behind close to a third of my collection. Most of those were Palladium books and esoteric GURPS books that I hadn't looked at in forever, but sometimes, I go to find a reference, and only then realize that it was in those stacks.
I also got rid of the SAGA system games (Dragonlance/Marvel Super Heroes). I had copies of the book for the Marvel system, but not the cards. Both of those have been hard to come by in good condition.
On the boardgame side, I've given away a lot of boardgames recently to my local library because of space concerns. But I haven't had anyone to play them with for a while- if I start to play again, I'm sure I'll miss something there, but I've been pretty methodical in the ones that I've given away, so I hope not.
Ascending Empires is the one for me. I got scared that the boards would warp and make the game unplayable, so I got rid of it. I think there's talk of a new release but nothing so far.
Quantum is another one, in part because the dice were degrading and leaving oil on the board. I should have waited longer to get a replacement set of dice, but I thought for sure my FLGS would get another copy in. Ah well.
Not one specific item.... but I did have to give up my entire rather extensive collection of 1970s/1980s gaming materials during a period of 3 rapid moves in the late 80s. Lots of books, miniatures, magazines, zines and apas. It was a bad time for me financially and at one point I was living out of a backpack and a trunk, staying on friend's couches for 3 months after a housing situation collapsed. If you name it, I probably owned it, as had spent several years working in a bookstore/gaming store and had bought demo copies of everything we carried during that time.
I never went back to using miniatures after that....
I don't think I've given away many board games. A few where I had multiple versions of the same game, I've given away -- I had half a dozen different Risk sets and at least 2 or 3 monopolies; I've given many of those away and don't regret it, either because I have other edition(s) which work just fine (Risk) and/or because never playing it again would seriously not hurt my feelings at all (Monopoly).
I've sold / traded quite a few #ttRPG games. Many of those, I look back on with nostalgia and regret losing. But, honestly, I wouldn't be playing them now if I still had them, most likely. My RPG collection is too vast anyway.
I'm a hoarder. I don't give things away unless I'm really absolutely 100% sure I'm never even going to think about it. I do occasionally loan something out, though. Like GURPS Russia, which I loaned to a friend, and I have no idea who it was, and nobody seems to have it. Or maybe my brother had it? I should ask him.