Rescue and recycling - Getting the knight to unlock the door (by completing all the rescues) will cause the key locked gates to open without the use of the key, or at least the treasure one. not sure about the others
All deconstruction zones - They are often listed as construct zones on gate maps, as opposed to gremlin ones. and considering they gremlins are resistant to elemental which constructs are weak to, this could prove a deadly combination, especially on T3 stages.
zombie jumping attacks are too sensitive, they seem to hit, even though they appear to not be touching you