As long as X is in X's owner's opponent's hand, X's owner may cast X and activate X's abilities. That opponent can't cast X and plays with their hand revealed.
{U}{B}, {T}: Put X into target opponent's hand.
{3}{U}{B}: You may play a land or cast a spell from the hand X is in. If you cast a spell this way, you cast it without paying its mana cost.

Psychic Network

Each player plays with the top card of their library held against their forehead, revealed to each other player.

Hazmat Suit (Used)

Enchant creature
Enchanted creature gets +2/+1 and has menace.
Whenever a player's skin or fingernail touches enchanted creature, that player loses 2 life.

Bureaucracy

Pursuant to subsection 3.1(4) of Richard's Rules of Order, at the beginning of the upkeep of each participant in this game of the Magic: The Gathering® trading card game (hereafter known as "PLAYER"), that PLAYER performs all actions in the sequence of previously added actions (hereafter known as "ACTION QUEUE"), in the order those actions were added, then adds another action to the end of the ACTION QUEUE. All actions must be simple physical or verbal actions that a player can perform while sitting in a chair, without jeopardizing the health and security of said PLAYER.
When any PLAYER does not perform all the prescribed actions in the correct order, sacrifice Bureaucracy and said PLAYER discards their complement of cards in hand (hereafter known as "HAND").

Kindslaver

{5}, {T}, Sacrifice Kindslaver: A person outside the game controls target player during that player's next turn. Neither player may advise that person until the end of that turn.

Spy Eye

Flying
Whenever Spy Eye deals combat damage to a player, you may draw a card from that player's library.

Checks and Balances

Cast this spell only if there are three or more players in the game.
Whenever a player casts a spell, each of that player's opponents may discard a card. If they do, counter that spell.

Masterful Ninja

Haste
Reveal Masterful Ninja from your hand: Masterful Ninja is on the battlefield and in your hand until end of turn.
{1}{B}: Masterful Ninja gets +1/+1 until end of turn.

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.

Denied!

Choose a card name, then target spell's controller reveals their hand. If a card with the chosen name is revealed this way, counter that spell.

Phoebe, Head of S.N.E.A.K.

Phoebe, Head of S.N.E.A.K. can't be blocked by creatures with flavor text.
{2}{U}{B}: Phoebe permanently steals target creature's text box. (That creature loses all rules text, flavor text, and watermarks. This creature gains them.)

Sly Spy

Whenever Sly Spy deals combat damage to a player, you may destroy target creature facing right in its art. (Creatures without faces don't face anywhere.)

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.

Gitaxian Probe

({U/P} can be paid with either {U} or 2 life.)
Look at target player's hand.
Draw a card.

Summon the Pack

Open a sealed Magic booster pack, reveal the cards, and put all creature cards revealed this way onto the battlefield under your control. They're Zombies in addition to their other types. (Remove those cards from your deck before beginning a new game.)

Sorry

Before any player casts a spell with the same name as a card in any graveyard, that player may say "sorry." If they don't, any other player may say "sorry" as the spell is being cast. When another player says "sorry" this way, counter the spell.
Whenever a player says "sorry" at any other time, Sorry deals 2 damage to that player.