Groundbreaker
Groundbreaker is a fictional character from the Transformers series. He is an Autobot Pretender.
Transformers: Generation 1
Groundbreaker is a Pretender Autobot who turns into a rocket car which can reach speed of mach 1. He his a mech of action who wants everything done now and is happy to be the one to do it. He is also brutally honest. His shell has a laser shield which can protect him from all but the most powerful attacks, but it also drains a lot of his power to keep the shield up.
Comics
Dreamwave Productions
Groundbreaker did not appear in any fiction from Dreamwave Productions, but did get a one page biography in their "More Than Meets The Eye" series.
IDW Publishing
In "Stormbringer Part 1" Groundbreaker is stationed on board the Autobot Orbital Command Hub, eagerly awaiting the call to battle.
Cloudburst, Groundbreaker, Landmine and Waverider appear in Spotlight: Hardhead investigating the Benzuli Expanse and reporting to Jetfire.
Marvel Comics
Although not seen or mentioned directly, Groundbreaker was among the Autobots who joined Fortress Maximus in leaving Cybertron for the planet Nebulos (Transformers: Headmasters #1). Unfortunately, they were followed to Nebulos by the Decepticons under Scorponok, leading war to break out once more. Fortress Maximus's band left Nebulos for the planet Earth, with the Decepticons in close pursuit. (Transformers: Headmasters #4).