So first off let me say that I love the fact that when building your deck your cards automatically trigger and the idea that you can't purposefully hold cards in reserve for in case the opponent plays a big attack. This being said I think it would be pretty sweet to have some epic level cards that allows a slight manipulation of the rules or allows for cards to be withheld in certain instances (I am thinking of some sort of trait card with a duration of 2 or something).
Off the top of my head, the only card I can think of that "breaks" the regular rules is Officer's Harness, specifically the rule about keeping a maximum of two cards to carry over into the next round. The Officer's Harness doesn't count towards that limit.
There's been mention of the devs holding back cards that would have card manipulation work differently - I think it was based on your discard pile et c. We don't know much more, but it's possibly related to Rogues, as that's the class they're holding back - and they seemed to want it to be something special.
Interesting. I managed to just get past unlocking The Goblin Bazaar in beta. Never came across that card even through the shops.
I have seen Mind Worm and I use Officer's Harness. I like the idea that they are holding things back for latter release too. Iron them out and check some balancing before releasing them. Because anything along the lines of what I am mentioning here is pretty powerful. I was also reading a thread yesterday about how if someone passes and then you use a card with cantrip then pass then you get to go first on the next round (still searching for that thread again and when I find it I will edit this post and add it in).