Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

First Day of Class

Whenever a creature you control enters this turn, put a +1/+1 counter on it and it gains haste until end of turn.
Learn. (You may reveal a Lesson card you own from outside the game and put it into your hand, or discard a card to draw a card.)

Grapeshot

Grapeshot deals 1 damage to any target.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Blaze Commando

Whenever an instant or sorcery spell you control deals damage, create two 1/1 red and white Soldier creature tokens with haste.

Answered Prayers

Whenever a creature you control enters, you gain 1 life. If Answered Prayers isn't a creature, it becomes a 3/3 Angel creature with flying in addition to its other types until end of turn.

Nurturing Presence

Enchant creature
Enchanted creature has "Whenever a creature you control enters, this creature gets +1/+1 until end of turn."
When Nurturing Presence enters, create a 1/1 white Spirit creature token with flying.

Suture Priest

Whenever another creature you control enters, you may gain 1 life.
Whenever a creature an opponent controls enters, you may have that player lose 1 life.