Madness —
Sorcery (C)
Target creature becomes deranged until your next turn. (That creature attacks a random player each combat if able for as long as it's deranged. It can attack its controller.)

Rejuvenator Elite
Creature - Elf Druid (U)
: Energize 2. Activate this ability only once each turn. (To energize 2, untap two permanents with the highest converted mana cost among tapped permanents you control.)
0/3

Fractured Scalding Tarn
Land (C)
Fractured Scalding Tarn enters the battlefield tapped.
: Add or
Fractured (You may mail twenty Fractured Scalding Tarns to Wizards of the Coast and receive a Scalding Tarn from the Fractured Expansion as redemption.)

Mick, the Bloodhound
Legendary Creature - Hound Warrior (R)
Grit (As long as a creature you control without grit is attacking, prevent all combat damage that would be dealt to this creature.)
Mick, the Bloodhound must be blocked if able.
No one's quite sure which side of the law he's on, and no one's brave enough to ask.
4/2

Gilded Golem —
Artifact Creature — Golem
Improvise
When Gilded Golem dies, create two colorless Gold artifact tokens with "Sacrifice this artifact: Add ."
, Exile Gilded Golem from your graveyard: Draw a card.
From talent comes money. From money comes power. From power comes the knowledge to rule the world.
2/2

Eight-and-a-Half Knives -
Legendary Creature - Fox Spirit Rogue
Juggler (You may attach and unattach Equipment from this creature whenever you could cast an instant)
As long as Eight-and-a-Half Knives is equipped, it has first strike.
Whenever Eight-and-a-Half Knives loses first strike, you may have it deal 1 damage to target attacking or blocking creature.
2/2

Predatory Carnosaur

Creature -- Dinosaur (R)
Killer (: This creature fights target creature you don't control. Activate this ability only as a sorcery, and only once.)
"I should've stayed in Argenport." --Karth, crownwatch deserter
7/7

Wouldn't a more direct translation cost ?

Professor Graytail
Legendary Creature - Viashino Wizard (M)
Learn (Whenever you cast a noncreature spell, if its converted mana cost is greater than this creature's power, put a +1/+1 counter on this creature.)
Whenever you cast an instant or sorcery spell, if its converted mana cost is less than or equal to Professor Graytail's power, copy that spell. You may choose new targets for the copy.
"Oh, I know this one."
1/3

Vainglorious Schemer
Creature - Human Advisor
Mustache-Twirling (If this creature would deal lethal damage to a creature or planeswalker, instead exile that permanent until this creature leaves the battlefield.)

"At last we meet. Unfortunately, we have little time to get acquainted, as you will soon be dead. It's nothing personal, of course. Your death simply serves my plans. What plans, you say? Well..."
5/5

Oops. Yeah, it would. It would also need a way to let it activate around summoning sickness.

Neural Pathway

Instant (U)
Draw two cards.
Network (You may cast a spell with the same name as this spell from your hand without paying its mana cost.)

Coming Storm
Sorcery (U)
Coming Storm deals 3 damage to any target.
Omen — You may reveal this card as you draw it. When you do, it deals 1 damage to any target.

Stripehusk Reverent
Creature - Insect Priest (U)
Reach
Piety - Whenever you cast a creature spell with in its mana cost, you may have it enter the battlefield with a +1/+1 counter on it for each in its mana cost.
2/3

Sultai Sidewinder
Creature - Naga Rogue (C)
Quick (This creature has first strike as long as it's unblocked.)
Whenever Sultai Sidewinder deals combat damage to a player, target creature an opponent controls gets -1/-1 until end of turn.
3/2

I don't like that this ability does basically nothing on its own, but Q is a hard letter.

Sudden Spate
Instant
Return all creatures without Flying to their owner's hand.
Remanence (When you cast this spell, if this card would go to a graveyard this turn, instead exile it then put it onto the battlefield flipped.)
///
Persistent Flood
Enchantment
All lands are Islands in addition to their other types.

Amphin Cutpurse

Creature -- Salamander Rogue (U)
Slippery 1 (This creature can't be blocked unless the defending player pays .)
Whenever Amphin Cutpurse deals combat damage to a player, draw a card.
2/1

Corpsewheel -
Artifact
, Sacrifice a creature: Corpsewheel becomes a 5/5 black artifact creature until end of turn.
Threshold - As long as seven or more cards are in your graveyard, Corpsewheel is a 5/5 black artifact creature.

Watch Captain Slate
Legendary Creature - Human Soldier (R)
First strike
Unite (Whenever you attack or block with every creature you control, this creature gets +1/+1 until end of turn.)
Whenever one or more creatures attack you, you may untap all creatures you control. If you do, creatures you control block this turn if able.
3/2

Bonebreaker Broker

Creature -- Ogre Rogue (C)
Vested (When this enters the battlefield, you may exile a card from your hand for as long as this remains on the battlefield.)
Whenever Bonebreaker Broker deals combat damage while it's vested, that player discards a card.
3/3