Sly Spy

Whenever Sly Spy deals combat damage to a player, that player loses a finger until Sly Spy leaves the battlefield. (The finger is chosen by its owner and can't roll dice or touch cards.)

Hangman

As Hangman enters, secretly note a word with six to eight letters.
{1}: Target player who doesn't control Hangman guesses the noted word or an unguessed letter in that word. If they guess wrong, put a +1/+1 counter on Hangman. Any player may activate this ability.
When a player guesses the noted word or all of its letters, sacrifice Hangman.

"Brims" Barone, Midway Mobster

When "Brims" Barone, Midway Mobster enters, put a +1/+1 counter on each other creature you control that has a hat.
"Brims" Barone, Midway Mobster has menace as long as you're wearing a hat.

Plains

Hat Trick

Target blocking or blocked creature you control gets +1/+1 and gains first strike until end of turn. If it has a hat, it gains double strike until end of turn. If you and that creature each have a hat, the creature gains triple strike until end of turn.

Rat in the Hat

{T}, Sacrifice Rat in the Hat: Until end of turn, you may cast target creature card that has a hat from your graveyard.

Swamp

Haberthrasher

Deathtouch
Whenever another creature you control that has a hat enters or a hat sticker is put on a creature you control, each opponent loses 1 life.