Splinter, Radical Rat

If a triggered ability of a Ninja creature you control triggers, that ability triggers an additional time.
{1}{U}: Target Ninja can't be blocked this turn.

Ravenous Robots

Whenever you cast an artifact spell, create a 1/1 colorless Robot artifact creature token.
{R}, {T}: Creature tokens you control gain haste until end of turn.

Northampton Farm

{T}: Add {C}.
{1}, {T}: Exile target creature you own.
{2}, {T}, Sacrifice this land: Return a creature card exiled with this land to the battlefield under your control. Return each other card exiled with this land to its owner's hand.

Continue?

Choose up to four target creature cards in your graveyard that were put there from the battlefield this turn. Return them to the battlefield.

Lessons from Life

Draw three cards. You may put a land card from your hand onto the battlefield tapped.

Ninja Pizza

Foods you control have "{T}, Sacrifice this artifact: Add one mana of any color."
At the beginning of your second main phase, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")

Sewer-veillance Cam

Flash
When this artifact enters or leaves the battlefield, you may tap or untap target creature.
{3}{U}, Sacrifice this artifact: Draw two cards.

Cool but Rude

(Gain the next level as a sorcery to add its ability.)
Whenever you attack, you may discard a card. If you do, draw a card.
{1}{R}: Level 2
Whenever you discard a card, this Class deals 2 damage to each opponent.
{1}{R}: Level 3
When this Class becomes level 3, search your library for a card, put it into your hand, shuffle, then discard a card at random.

Frog Butler

Deathtouch
{T}: Add one mana of any color.
{2}: This creature gains reach until end of turn.

Improvised Arsenal

Equipped creature gets +1/+0 for each artifact you control.
{4}{R}: Create a token that's a copy of this Equipment.
Equip {R}

Michelangelo, Weirdness to 11

When Michelangelo enters, create a Mutagen token. (It's an artifact with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")
If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.

Kitsune's Technique

Sneak {1}{U} (You may cast this spell for {1}{U} if you also return an unblocked attacker you control to hand during the declare blockers step.)
Target opponent mills half their library, rounded up.

Shredder's Technique

Sneak {B} (You may cast this spell for {B} if you also return an unblocked attacker you control to hand during the declare blockers step.)
Destroy target creature or enchantment. If an enchantment was destroyed this way, you lose 2 life.

Anchovy & Banana Pizza

When this artifact enters, destroy target creature.
{2}, {T}, Sacrifice this artifact: You gain 3 life.

Endless Foot Assault

Squad {1}{W} (As an additional cost to cast this spell, you may pay {1}{W} any number of times. When this enchantment enters, create that many tokens that are copies of it.)
Whenever you attack, for each opponent, create a 1/1 black Ninja creature token that's tapped and attacking that player.

Mutagen Man, Living Ooze

Trample
Activated abilities of artifact tokens you control cost {1} less to activate.
When Mutagen Man enters, create X Mutagen tokens. (They're artifacts with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")