These are the cards in this life gaining combo:
 
Confessor
Cost: 1 White
Creature
Card text: Whenever a player discards card from his or her hand, you may gain
1 life. 1/1
 
Tireless Tribe
Creature
Cost: 1 White
Card text: Discard a card from your hand: Tireless Tribe gets +0/+4 until end
of turn.
1/1
 
Animal Boneyard
Enchant Land
Costs: 2 Colorless and 1 White
Card text: Enchanted land has "Tap, Sacrifice a creature: You gain life equal
to that creature's toughness."
 
If you have about 4 of each of these in your deck heres what you can do. If
you have at least one Tireless Tribe out in play and a couple of confessors
and at least 6-7 cards in your hand, you can discard all those cards and gain
one life for each card discarded times the number confessors you have while
giving Tireless Tribe around +0/+28, then sacrifice Tireless Tribe with
Animal Boneyard and gain an extra 29 life.
That's a total of around 57 life if you had 7 cards in your hand and 4
Confessors out.