Pit Fight

Target creature you control fights another target creature. (Each deals damage equal to its power to the other.)

Burning-Tree Emissary

When Burning-Tree Emissary enters, add {R}{G}.

Halo Hopper

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)

Horned Kavu

When Horned Kavu enters, return a red or green creature you control to its owner's hand.

Ram Through

Target creature you control deals damage equal to its power to target creature you don't control. If the creature you control has trample, excess damage is dealt to that creature's controller instead.

Lead the Stampede

Look at the top five cards of your library. You may reveal any number of creature cards from among them and put the revealed cards into your hand. Put the rest on the bottom of your library in any order.

Prizefight

Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)
Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Mardu Scout

Dash {1}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)