[10] Every Pokmon card has a symbol on the bottom that indicates its rarity, so some gold cars are more rare than others
This won't touch generic mana costs or other colors, and it only works on permanents, which was clearly done to keep them from getting broken by casting free Brainstorms, counters, Lightning Bolts, Swords to Plowshares, etc
This means that if you cast Syphon MindSyphon Mind each other player will discard a card and the caster draws for everyone, not just the enemy players opposite that player
The problem with pure creature tutor cards is that they only find one part of your combo, in most cases you are just better off running another threat than a tutor
Ken gets a lot of extra millage from double strike
Skullclamp is particularly famous for the seemingly-innocuous change during development from granting +1/+2 to +1/-1, while also reducing the Equip cost to a single mana