The Pipe Wrench is depicted as a large red 20" heavy duty wrench that can be used as a melee weapon.
The weapon originally appeared in Grand Theft Auto V, where it is only used in the mission By The Book as a choice of a torture weapon, but is practically unable to be used in free-roam. Said weapon is depicted in the Rockstar Games Social Club renders, confirming its appearance as a weapon.
Grand Theft Auto Online
Being a large and heavy tool, the Pipe Wrench can knock NPCs quickly and is used with a single hand, allowing for fast attacks.