Miles "Tails" Prower

Flash
Flying
Whenever a Vehicle you control enters, draw a card if it has flying. Otherwise, put a flying counter on it.

Floodpits Drowner

Flash
Vigilance
When this creature enters, tap target creature an opponent controls and put a stun counter on it.
{1}{U}, {T}: Shuffle this creature and target creature with a stun counter on it into their owners' libraries.

Nova Hellkite

Flying, haste
When this creature enters, it deals 1 damage to target creature an opponent controls.
Warp {2}{R} (You may cast this card from your hand for its warp cost. Exile this creature at the beginning of the next end step, then you may cast it from exile on a later turn.)

Ethersworn Shieldmage

Flash
When this creature enters, prevent all damage that would be dealt to artifact creatures this turn.

Razorkin Hordecaller

Haste
Whenever you attack, create a 1/1 red Gremlin creature token.

Thundering Giant

Haste (This creature can attack and {T} as soon as it comes under your control.)

Knuckles the Echidna

Double strike, trample, haste
Whenever one or more creatures you control deal combat damage to a player, create a Treasure token.
Treasure Hunter — At the beginning of your upkeep, if you control thirty or more artifacts, you win the game.

Frantic Scapegoat

Haste
When this creature enters, suspect it. (It has menace and can't block.)
Whenever one or more other creatures you control enter, if this creature is suspected, you may suspect one of the other creatures. If you do, this creature is no longer suspected.

Sonic the Hedgehog

Haste
Gotta Go Fast — Whenever Sonic the Hedgehog attacks, put a +1/+1 counter on each creature you control with flash or haste.
Whenever a creature you control with flash or haste is dealt damage, create a tapped Treasure token.

Sunpearl Kirin

Flash
Flying
When this creature enters, return up to one other target nonland permanent you control to its owner's hand. If it was a token, draw a card.

Mischievous Pup

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, return up to one other target permanent you control to its owner's hand.

Flamewake Phoenix

Flying, haste
This creature attacks each combat if able.
Ferocious — At the beginning of combat on your turn, if you control a creature with power 4 or greater, you may pay {R}. If you do, return this card from your graveyard to the battlefield.

Cathar Commando

Flash
{1}, Sacrifice this creature: Destroy target artifact or enchantment.

Riverwheel Sweep

Tap target creature. Put three stun counters on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Exile the top two cards of your library. Choose one of them. Until the end of your next turn, you may play that card.