BeckJack in Super Mario 64 is a ROM hack or custom modification of the popular Nintendo 64 game. It replaces Mario with a character named BeckJack, altering the gameplay experience to reflect the character's abilities and the modder's vision.  This is fan-made content, not an official Nintendo product, and features custom elements within the original Super Mario 64 engine.

BeckJack in Super Mario 64

BattleTanx - Global Assault (USA)