Gruul Beastmaster

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Whenever Gruul Beastmaster attacks, another target creature you control gets +X/+0 until end of turn, where X is Gruul Beastmaster's power.

Compelled Duel

Target creature gets +3/+3 until end of turn and must be blocked this turn if able.

Forest

Bonesplitter

Larger Than Life

Target creature gets +4/+4 and gains trample until end of turn.

Champion of Lambholt

Creatures with power less than Champion of Lambholt's power can't block creatures you control.
Whenever another creature you control enters, put a +1/+1 counter on Champion of Lambholt.

Soul's Might

Put X +1/+1 counters on target creature, where X is that creature's power.

Hardy Outlander

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, another target creature you control gets +X/+X until end of turn, where X is this creature's power."

Syr Faren, the Hengehammer

Whenever Syr Faren, the Hengehammer attacks, another target attacking creature gets +X/+X until end of turn, where X is Syr Faren's power.

Blanchwood Armor

Enchant creature
Enchanted creature gets +1/+1 for each Forest you control.

Wild Beastmaster

Whenever Wild Beastmaster attacks, each other creature you control gets +X/+X until end of turn, where X is Wild Beastmaster's power.