Impassioned Orator

Whenever another creature enters the battlefield under your control, you gain 1 life.

Rhox Faithmender

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
If you would gain life, you gain twice that much life instead.

Plains

Crib Swap

Changeling (This card is every creature type.)
Exile target creature. Its controller creates a 1/1 colorless Shapeshifter creature token with changeling.

Baneslayer Angel

Flying, first strike, lifelink, protection from Demons and from Dragons

Cleric Class

(Gain the next level as a sorcery to add its ability.)
If you would gain life, you gain that much life plus 1 instead.
{3}{W}: Level 2
Whenever you gain life, put a +1/+1 counter on target creature you control.
{4}{W}: Level 3
When this Class becomes level 3, return target creature card from your graveyard to the battlefield. You gain life equal to that creature's toughness.

Cradle of Vitality

Whenever you gain life, you may pay {1}{W}. If you do, put a +1/+1 counter on target creature for each 1 life you gained.

Daxos, Blessed by the Sun

Daxos's toughness is equal to your devotion to white. (Each {W} in the mana costs of permanents you control counts toward your devotion to white.)
Whenever another creature you control enters the battlefield or dies, you gain 1 life.

Felidar Sovereign

Vigilance, lifelink
At the beginning of your upkeep, if you have 40 or more life, you win the game.