Who is Jack Tack?

Jack Tack isn't actually a "who," Jack Tack is an "It."

Jack Tack is short for Jackrabbit Tack, which is the second best jumping tack on the game HorseIsle. You can go to the library in any town that has one. Go under Research Tack, then scroll down until you see Jackrabbit Tack. Hit View, then take a peek at it!