My least favorite rule-set would be those that you can use only odd or even mana cards, because they limit my choices a lot, specially in low mana battles, they are very constraining rule-sets. My favorite could it be the Earthquake one, although, I don't always win, but it's amazing how you see the cards fall one by one, specially when you don't pay attention and you are not using flying cards. Have you noticed how many people don't pay attention to the rule-sets? Thank you again for your wonderful giveaways!