I was thinking of cards that cause people in tournaments to call judges due to: awkward game states, confusing oracle text, and just being so obscure for future deck creation ideas. I always like seeing people go: "It does what now?" when they see a card. I got someone to say that playing a Japanese Empyrial Archangel since Reanimator uses Inkwell Leviathan for the shroud fatty.

So far cards I can think of are:

Chains of Mephistopheles
Humility
Opalescence