Cards that remove or suppress abilities are extremely useful in this format when used to target commanders.

Goreclaw, Terror of Qual Sisma: 1
CC: 3G
P/T: 4/3
Reduces CC by 2 for creatures with POWER >= 4
When Goreclaw attacks, each creature you control w/ power > 4 gets +1/+1 and gains trample U.E.o.T.

Notes: When Goreclaw attacks, it is effectively a 5/4 with trample. This pairs nicely with Yeva, Nature's Herald, Rhonas the Indomitable, and Molimo!

Rhonas the Indomitable:
CC: 2G
P/T: 5/5
Deathtouch, Indestructible
Rhonas can't attack or block unless you control another creature with power >= 4.
2G: Another target creature gets +2/+0 and gains trample U.E.o.T.

Notes: Not hard to get Rhonas to the point where it can attack and block. The mana ability can be played on opponents creatures when they are attacking another opponent.
Notes: Goreclaw is effectively a 5/4 with trample when he attacks.

Hazoret the Fervent:
CC: 3R
P/T: 5/4
Indestructible, Haste
Hazoret can't attack or block unless you have one or fewer cards in hand.
2R, Discard a card: Hazoret deals 2 dmg to each opponent.

Notes: Need lots of mana and the ability to draw cards to make the DD work.

Kamahl, Pit Fighter:
CC: 4RR
P/T: 6/1
Haste
Tap: Kamahl deals 3 dmg to tgt creature or player.

Notes: If you had a way to untap Hamahl, you could really run away with the game. Otherwise, he could kill in 6 turns after being cast. Haste makes makes it so that he is still effective even when targeted by removal spells.

Molimo, Maro-Sorcerer:
CC: 4GGG
P/T: */*
Trample
Molimo's power and toughness are each equal to the number of lands you control (min. 7/7)

Notes: Molimo does not provide any advantages for the rest of your board.

Nefarox, Overlord of Grixis:
CC: 4BB
P/T: 5/5
Flying
Exalted (creatures you control that attack alone get +1/+1 U.E.o.T.)
Whenever Nefarox attacks alone, defending player sacrifices a creature.

Notes: Could be paired with spells that have enters the graveyard abilities. Effectively a 6/6 Flier when Nefarox attacks alone. Almost guaranteed to do D.D. or at least survive when it attacks. Exalted is not really useful for the rest of your creatures.

Yeva, Nature's Herald:
CC: 2GG
P/T: 4/4
Flash
You may cast green creatures as if they had flash.

Notes: Unless you have a way to untap mana or otherwise reduce casting cost of your creatures, the ability to cast big green creatures in you opponent's turn (Flash) isn't very productive except as combat trick blocking. On the other hand, if you bluff on subsequent turns, your opponent may be a lot less inclined to attack. Playing against something like Deathtouch would shut you down as far as this strategy is concerned.