Cheapest priced copy (Battle for Zendikar): $0.35 at Card Kingdom, near mint, their price list as of .
Reckless Cohort 
Creature — Human Warrior Ally · 2/2 · Common · Battle for Zendikar · #152
This creature attacks each combat if able unless you control another Ally.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Battle for Zendikar | 152 | Common | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 25 August 2015Reckless Cohort can attack if you control another Ally. It just isn’t forced to.
- 25 August 2015If, during its controller’s declare attackers step, that player doesn’t control another Ally but Reckless Cohort is tapped, is affected by a spell or ability that says it can’t attack, or hasn’t been under that player’s control continuously since the turn began (and doesn’t have haste), then it doesn’t attack. If there’s a cost associated with having Reckless Cohort attack, its controller isn’t forced to pay that cost. If they don’t, Reckless Cohort doesn’t have to attack.
- 25 August 2015Reckless Cohort checks whether you control another Ally as attacking creatures are declared. At that time, if you don’t, Reckless Cohort attacks if able.