Briarhorn

Flash
When this creature enters, target creature gets +3/+3 until end of turn.
Evoke {1}{G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

The List

Duel Decks: Nissa vs. Ob Nixilis

Flash (You may cast this spell any time you could cast an instant.)
When Briarhorn enters the battlefield, target creature gets +3/+3 until end of turn.
Evoke {1}{G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters the battlefield.)

Duel Decks: Ajani vs. Nicol Bolas

Planechase

Lorwyn

Flash
When Briarhorn comes into play, target creature gets +3/+3 until end of turn.
Evoke {1}{G} (You may play this spell for its evoke cost. If you do, it's sacrificed when it comes into play.)

If you cast this card for its evoke cost, you may put the sacrifice trigger and the regular enters-the-battlefield trigger on the stack in either order. The one put on the stack last will resolve first.