Avenger of Zendikar

When Avenger of Zendikar enters, create a 0/1 green Plant creature token for each land you control.
Landfall — Whenever a land you control enters, you may put a +1/+1 counter on each Plant creature you control.

Aggressive Biomancy

Create X tokens that are copies of target creature you control, except they have "When this creature enters, it fights up to one target creature you don't control."

Academy Manufactor

If you would create a Clue, Food, or Treasure token, instead create one of each.

Apothecary Stomper

Vigilance (Attacking doesn't cause this creature to tap.)
When this creature enters, choose one —
• Put two +1/+1 counters on target creature you control.
• You gain 4 life.

Aether Channeler

When Aether Channeler enters, choose one —
• Create a 1/1 white Bird creature token with flying.
• Return another target nonland permanent to its owner's hand.
• Draw a card.

Bakersbane Duo

When Bakersbane Duo enters, create a Food token.
Whenever you expend 4, Bakersbane Duo gets +1/+1 until end of turn. (You expend 4 as you spend your fourth total mana to cast spells during a turn.)

Aggressive Mammoth

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Other creatures you control have trample.

Adrix and Nev, Twincasters

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
If one or more tokens would be created under your control, twice that many of those tokens are created instead.