Free - Galactic Hitman

Here's an informational link about it: https://www.reddit.com/r/Steam/comments/5rqv0s/community_items_for_banned_games_are_now/

And here's a link that contains a list of some market-banned games, including this one: https://steamcommunity.com/groups/card-trading-card-trades/discussions/1/133255957994868314/

https://steamcommunity.com/groups/card-trading-card-trades/discussions/1/133255957994868314/
Developer's games were removed by Valve because of breaking rules (DH harassing users, others using alt accounts to vote up their games, etc) have their cards, emoticons and backgrounds set to non-marketable

https://www.steamgifts.com/discussion/7WTiu/digital-homicides-cards-are-now-non-marketable
Basically whoever's game(s) were removed from Steam because breaking rules, the cards were made non-marketable.
can't find a proper valve-news about it, but situation is explained here https://steamcommunity.com/groups/card-trading-card-trades/discussions/1/133255957994868314/

See my post in the comment above for links. :)

Edit: Or the link above that adam just posted.

Oh yes, this one. I'll edit it, you're correct

I think they don't have a bloody idea what's going on around them.
Them suing a critic for criticizing and defaming while they actually did attack him personally, they tried to sue the ~100 anonymous steam users because not liking their games, most of them were based on nicknames not proper steam urls... they have a weird connection with reality.