Cannonball Runner

Cannonball Runner is a Level 42 quality Trinket that summons a automated cannon that will fire upon enemies in front of it that you are in combat with.

Source
This item drops from Willey Hopebreaker in the Stratholme Main Gate wing.

Trivia

 * It's name is based on the illegal cross-country race, the Cannonball Baker Sea-To-Shining-Sea Memorial Trophy Dash, which led to a series of films with Burt Reynolds.