Ferocious Pyro, it gains +2AP for the small cost of one more red energy a turn. Seemingly weak (with the stats 1AP/1HP), it's underestimated by many. It's a great defender, though, as well as a good attacker-- just use the ability when you need it, and Mischievous Pyro becomes something more than what it seems to be.
Strong against: slow-developing and quality decks, decks with low ally count.
Weak against: direct damage actions, Murderous Imp, ally-heavy decks.