Tracker | Magic: The Gathering
Formats Tracker is Legal in
Official Oracle Text for Tracker
Official Rulings for Tracker
10/4/2004 : If this leaves the battlefield before its activated ability resolves, it will still deal damage to the targeted creature. On the other hand, if the targeted creature leaves the battlefield before the ability resolves, the ability will be countered and no damage will be dealt.
10/1/2009 : You may have Tracker target itself with its own ability. If you do, Tracker will deal damage to itself equal to its power, then immediately do it again.