I'm not sure there is such a thing as a player who is unavailable for ANY trade, but here's my listing of what it would take:
Franz, Paolo, Markelle, Wendell - if you want one of them you better be including a multi-time all-star under 30y.o. to even start the discussion.
Isaac is about the same if he stays healthy the rest of the season.
These next guys I would like to keep, but the right package of players in the 22-25y.o. range and/or draft picks could sway me.
I really like Harris, but again, he needs to stay healthy the rest of the season. Moe Wagner is tough, because I think he is more valuable to us than to anyone else.
I would like to give Okeke, Suggs, & Houstan more time to get healthy and/or develop, but they are negotiable.
Now we are getting down to guys that I would be okay with trading, individually or in some kind of package deal.
Cole is probably our most valuable, tradeable asset in terms of potential value. Unfortunately because of his rookie contract the best offers for him would have to be in conjunction with other (expiring?) players. If we could get more of the team concept into his head, he'd be worth keeping, but his strong tendency to descend into "hero ball" is concerning. It blows up into disaster as often as it results in a win. I do love his energy and enthusiasm, though.
Bol is an interesting player with a lot of good things on the offensive side, but he's detrimental on defense. He doesn't have the heft to play defense (right now?). Could that change? Maybe, but he has to stay healthy and put on some weight. He has a similar body type to his father, who never really could put on weight. Same value problem as Cole, his contract is cheap, so getting equal value would probably require a multi-player trade.
Bamba is one of those guys who looks so much better on paper than he does in actual games. How a guy his size can be so poor on defense and rebounding astounds me. He does enough well on the offensive end that someone might take a chance of him developing a more complete game. I hope we can turn him into other assets.
Ross is my most disappointing player this year. His offense has been even more inconsistent, and he seems to be falling out of the rotation. The torch lightings have been few and far between, and we don't seem to ride them when they do happen. He expires at the end of the season, so get whatever you can get now. Maybe package him with Cole or Bol to help offset salaries on a multi-layer deal.
RJ Hampton had a miserable pre-season, but I think he has actually played well when given the opportunity. I just don't have a good handle on what value to place on him. He is an expiring rookie contract - so again you would have to package him with other players to get decent value, or settle for picks. I think he would be more valuable to other teams than he is to us, but I'm not sure that anyone has seen enough to give us a decent offer. He's kind of been the lost guy this year.