Heavy weapons clone trooper
A clone heavy gunner clad in Phase II armor.
Heavy gunners, also referred to as heavy weapons clone troopers, functioned as specialized heavy weapon units within the Grand Army of the Republic.
Characteristics

These clone troopers carried the most devastating explosives and weaponry available to the army, such as missiles, grenades, demolition charges, and heavy cannons. The most sizable weapons ever intended for use by clone troopers were their primary armaments.
They featured a few missiles attached to their belts, targeting goggles positioned on their foreheads, and a communication device, along with robust shoulder and sharp knee guards. Their belts had three pouches on the front. Their boots had a more polished appearance, and they carried an Unidentified Missile Launcher (as depicted in the image on the right).
History
During the Battle of Utapau, numerous heavy gunners were present when Order 66 was executed. Three of these troopers were tasked with assassinating Obi-Wan Kenobi, but the Jedi Master instead killed them. Shortly after, during the Raid on the Jedi Temple on Coruscant, heavy gunners were sent into the Jedi Temple to destroy the ancient statues and pillars that supported the vaulted ceilings. These clones subsequently served in the Galactic Empire, becoming the heavily armed Imperial shock troopers.