All creatures able to block Nessian Boar do so.
Whenever Nessian Boar becomes blocked by a creature, that creature's controller draws a card.

Trample
Champion an Elemental (When this enters the battlefield, sacrifice it unless you exile another Elemental you control. When this leaves the battlefield, that card returns to the battlefield.)

Flying, lifelink, indestructible, haste

Trample
While you're searching your library, you may cast Panglacial Wurm from your library.

Annihilator 3 (Whenever this creature attacks, defending player sacrifices three permanents.)
Pathrazer of Ulamog can't be blocked except by three or more creatures.

Phyrexian Colossus doesn't untap during your untap step.
Pay 8 life: Untap Phyrexian Colossus.
Phyrexian Colossus can't be blocked except by three or more creatures.

Trample
When Phyrexian Dreadnought enters the battlefield, sacrifice it unless you sacrifice any number of creatures with total power 12 or greater.

Cumulative upkeep—Sacrifice a creature. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

When Phyrexian Triniform dies, create three 3/3 colorless Golem artifact creature tokens.
Encore (, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Your life total can't change. (You can't gain or lose life. You can't pay any amount of life except 0.)

Trample
Polar Kraken enters the battlefield tapped.
Cumulative upkeep—Sacrifice a land. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

When Primeval Force enters the battlefield, sacrifice it unless you sacrifice three Forests.

This spell costs less to cast for each creature your opponents control.
When Primeval Protector enters the battlefield, put a +1/+1 counter on each other creature you control.

Protection from everything
If Progenitus would be put into a graveyard from anywhere, reveal Progenitus and shuffle it into its owner's library instead.

When Pursued Whale enters the battlefield, each opponent creates a 1/1 red Pirate creature token with "This creature can't block" and "Creatures you control attack each combat if able."
Spells your opponents cast that target Pursued Whale cost more to cast.

Flying, trample
Pay 2 life, Sacrifice another creature: Search your library for a card and put that card into your hand. Then shuffle your library.

Vigilance

Enrage — Whenever Silverclad Ferocidons is dealt damage, each opponent sacrifices a permanent.