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.

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.

Gruul Beastmaster

Riot (This creature enters the battlefield 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.