Authority of the Consuls

Creatures your opponents control enter tapped.
Whenever a creature an opponent controls enters, you gain 1 life.

Diamond Mare

As this creature enters, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Righteousness

Target blocking creature gets +7/+7 until end of turn.

Nyx-Fleece Ram

At the beginning of your upkeep, you gain 1 life.

Ajani's Welcome

Whenever a creature you control enters, you gain 1 life.

Impassioned Orator

Whenever another creature you control enters, you gain 1 life.

Linden, the Steadfast Queen

Vigilance (Attacking doesn't cause this creature to tap.)
Whenever a white creature you control attacks, you gain 1 life.

Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on this creature.

Plains

Twinblade Paladin

Whenever you gain life, put a +1/+1 counter on this creature.
As long as you have 25 or more life, this creature has double strike. (It deals both first-strike and regular combat damage.)