Goblin Rabblemaster

two generic mana one red mana Creature — Goblin WarriorPower and toughness2/2

Other Goblin creatures you control attack each combat if able.

At the beginning of combat on your turn, create a 1/1 red Goblin creature token with haste.

Whenever this creature attacks, it gets +1/+0 until end of turn for each other attacking Goblin.

Showing Magic 2015#145

Price

0.89 $

Foil 4.38 $

32 printings · up to 7.84 $

Daily estimate from Scryfall, not a shop quote.

2014-07-18
Although Goblin Rabblemaster doesn't force itself to attack, if you control two of them, they'll force each other to attack if able.
2014-07-18
If, during your declare attackers step, a creature that must attack if able is tapped, is affected by a spell or ability that says it can't attack, or hasn't been under your control continuously since the turn began (and doesn't have haste), then it doesn't attack. If there's a cost associated with having a creature attack, you're not forced to pay that cost, so it doesn't have to attack in that case either.
2014-07-18
The number of attacking Goblins is counted as the last ability resolves, and the bonus is locked in at that time.