Slaying Mantis

Just a second (As long as this spell is on the stack, players can't move permanents.)
Slaying Mantis enters by being thrown from a distance of at least three feet.
When Slaying Mantis enters, it fights each creature an opponent controls that it touched as it entered.

Better Than One

A person outside the game becomes your teammate. (Choose any number of cards in your hand, on top of your library, or on the battlefield under your control. Those cards become your teammate's hand, library, and permanents, respectively.)

Boomstacker

As Boomstacker enters and whenever it attacks, stack two dice on top of it. (All dice must be stacked vertically, one on top of another.)
Boomstacker gets +1/+1 for each die in its stack.
Boomstacker attacks each combat if able.
When the stack falls, sacrifice Boomstacker.

Flavor Judge

{T}: Choose target spell or ability that targets a permanent you control. Then ask a person outside the game if the story of what will happen makes sense. If they say no, sacrifice Flavor Judge and counter that spell or ability.

Form of the Approach of the Second Sun

When this enchantment enters, you gain 7 life. You become a card until you leave your library or that library is shuffled. Put yourself seventh from the top, balancing the cards on top of you on your head.
When you draw yourself, you win the game.
When one or more cards fall off your head, exile them and all cards on your head, then sacrifice this enchantment.

Goblin Sleigh Ride

Target creature you control climbs into Goblin Sleigh Ride. You slide them on their merry way. If the creature stayed on, it deals damage equal to its toughness to each other creature touched during the slide.

"Ach! Hans, Run!"

At the beginning of your upkeep, you may say "Ach! Hans, run! It's the . . ." and the name of a creature card. If you do, search your library for a card with that name, put it onto the battlefield, then shuffle. That creature gains haste. Exile it at the beginning of the next end step.

Squirrel Dealer

When Squirrel Dealer enters, ask a person outside the game "Do you like Squirrels?" If they do, create a 1/1 green Squirrel creature token.

Devil K. Nevil

Haste
When Devil K. Nevil enters, jump it over any number of creatures. If it clears those creatures, put that many +1/+1 counters on it. (You can see a jumping demonstration at DevilKNevil.com.)

Side to Side

You and target opponent arm-wrestle. If you win, create a 3/3 green Ape creature token.