Ambiguity

Whenever a player plays a spell that counters a spell that has been played or a player plays a spell that comes into play with counters, that player may counter the next spell played or put an additional counter on a permanent that has already been played, but not countered.

Cheatyface

If Cheatyface is in your hand, you may sneak Cheatyface onto the battlefield. If an opponent catches you right away, that player may exile Cheatyface.
Flying

Big Boa Constrictor

When this creature enters, roll a six-sided die. Target opponent loses life equal to the result.

Common Courtesy

Whenever a player casts a spell without asking your permission while casting it, counter that spell.
When a player asks you permission to cast a spell and you refuse, counter that spell and sacrifice Common Courtesy.

Defective Detective

Defective Detective can't be blocked.
When Defective Detective enters, a person outside the game looks at target opponent's hand and chooses a card from it. That player reveals that card.

Chicken à la King

Whenever a 6 is rolled on a six-sided die, put a +1/+1 counter on each Bird. (You may roll dice only when instructed to.)
Tap an untapped Bird you control: Roll a six-sided die. (Like now.)

Animate Library

Enchant your library
Enchanted library is an artifact creature on the battlefield with power and toughness each equal to the number of cards in it. It's still a library.
If enchanted library would leave the battlefield, exile Animate Library instead.

Dirty Rat

When this creature enters, target opponent discards a card.

Clam-I-Am

If you roll a 3 on a six-sided die, you may reroll that die.

Clocknapper

When Clocknapper enters, choose beginning phase, first main phase, combat phase, postcombat main phase, or ending phase. Steal that phase from target player during their next turn. (That phase occurs as though it's your turn instead.)

Crafty Octopus

When this creature enters, this creature assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.)

B.F.M. (Big Furry Monster)

You must cast both B.F.M. cards to put
leaves the battlefield, sacrifice the other.
B.F.M. can't be blocked except by three or

capital offense

target creature gets -x/-x until end of turn, where x is the number of times a capital letter appears in its rules text. (ignore reminder text and flavor text.)

Censorship

As Censorship enters, choose a word.
Whenever a player says the chosen word, Censorship deals 2 damage to that player.