I was looking at deck ideas, and noticed that almost all of them are based on a creature type. I'm thinking of building a deck which is designed to punish players for having too many cards of the same color/creature type.
Here are some cards I'm considering that affect creature types:
An-Zerrin Ruins (1RR) Enchant - Creatures of a chosen creature type do not untap during untap step.
Artificial Evolution (U) Instant - Rewrite all instances of "X creature type" on a card with a different type.
Circle of Solace (3W) Enchant - (1W): Prevent damage dealt to you by a creature of X turn.
Engineered Plague (2B) Enchant - Creatures of chosen creature type get -1/-1
Extinction (4B) Sorcery - Destroy all creatues of chosen creature type.
Faces of the Past (2U) Enchant - Whenever creature dies, tap/untap all creatures of their type.
Steely Resolve (1G) Enchant - All creatures of X creature type have shroud.
Tsabo's Decree (5B) Instant - All creatues of X type are discarded from target player's hand and removed from their battlefield.
I also need to find some cards that affect chosen colors, and I might look for cards that destroy tokens or creatures with the same name.
Any suggestions?