I found a possible (but likely) bug in the game involving Santa Guise. If Argent Adept has presents in his play area, and he plays one of his instruments (or uses his base power), he's able to activate the effect on an unknown face down card.
Already reported, with screenshots. I forget where, though.
This will be fixed in the next update, thanks!
My screenshot was too large of a file 
But at least it's reported.
Mr. Fixer's tools can also trigger while face-down. I've already reported that one too. Specifically, I had Jackhammer in play and Dual Crowbars was face-down. Dual Crowbars triggered a second round of damage after my next attack.
Wow, Mr. Fixer has a Jackhammer? Wonder what it does? My guess is this: "Turn all damage done by Mr. Fixer into sonic damage, but only when the target wants peace and quiet" 
Heh, that's a weird slip to make…
I would suggest the Jackhammer's true ability is: "After Mr. Fixer does damage to an Environment Target, he deals 2 Sonic Damage to all non-Environment Targets." 
Nah, I have a better one. "When a villain card would prevent Mr. Fixer from dealing damage, he instead deals each villain target 1 Sonic damage, then deals each villain target 1 Sonic damage, then deals each villain target 1 Sonic damage, etc."