Non-Canon Alert! The subject of this article originates from non-canonical sources. To find out about what is considered "canon" see LOTR:Canon.
Guldur War Trolls also known as "Gundabad Trolls" were a large and stocky breed of "great" Olog-hai bred in the cesspits of Mount Gundabad. Along with Azog's orc legions, many of these large trolls congregated in the pits of Dol Guldur. Over a dozen of these Giants marched across central Middle Earth along with other forces of Sauron (namely orcs and wargs) To siege the previous dwarven stronghold of Erebor. These trolls were seen fighting against Dain and Thranduil's armies during the Battle of the Five Armies.
Along with co-participating catapult wielding Misty Mountain Trolls, these Ologs were also very large, dwarfing all the other troll/olog types seen previously, (about 25 to 30 feet tall or more) used as terror weapons and war beasts, these giant trolls were either given full or partial suits of crude yet durable iron armour. unlike the smaller yet extremely similar Guldur Olog-Hai (which were all fully armored,). During the battle of Erebor, these giant beasts devastated dozens of soldiers with one strike alone of their weapons, and caused massive havoc on the battlefield.
Unlike the smaller Guldur Olog-Hai, these trolls couldn't simply be taken down by a spear throw to the neck or a few arrows. It would take dozens of arrows and several spears/pikes to be sent into the unarmored parts of the troll in order to take it down. A premeditated attack upon a troll would usually work and needed to be planned out well in order to kill the creature.
Being Ologs, these trolls were quite intelligent and kept formation with the orcs as they marched to battle. The war trolls carried a variety of weapons into battle against the allied armies of dwarves, elves, and men. Some trolls carried huge scythed gauntlets fitted with huge and sharp blades. (similar to the Guldur Orcs' shields). Others carried steel war maces and huge wooden clubs fitted with iron spikes in order to smash men and elf alike into paste. Some even used their bare hands, balling them up into fists to smash the allied armies, a few just simply grabbed the allied soldiers and threw them across the battlefield.
Other than being huge shock troops during the great battle of Erebor, certain varieties and sub-species of great Ologs were used to Azog's advantages, by being given siege machinery (such as ladders or battering ram-like stone headpieces.
The least fortunate of these giant trolls was dubbed "Stumpy," by the producers. He was Albino, Truncated at the limbs, (chained flails replaced his arms, while wrecking ball-like maces were in place of his legs. Stumpy was born blind and eyeless, and had chains fixed from his eye sockets to a chair on his back that was controlled by an orc driver. During the film "The battle of the five armies: the extended edition" the large albino troll was seen smashing through both elf and dwarf lines, until he was hijacked by Bofur, and was made to fight against other trolls and orcs (unwillingly) on the way to Ravenhill and was ultimately killed by Legolas.
During the Battle of the Five Armies (Extended Edition only), a war troll was commandeered by Bofur, using the chains connected to its eye sockets to move it around. He used it to fight against the Guldur Orcs, until the other dwarves procured a dwarven battle cart and used it to smash through the army to get to Azog. Bofur followed them with his war troll until another war troll came across the other dwarves. Bofur controled his war troll to fight another war troll. The weight of the other war troll causes it to sink into the ice. Bofur and his troll begin to sink as well, until Bofur kills the other war troll using the one he is currently controlling. Bofur abandons his war troll and goes with the others, while the war troll wanders off aimlessly, smashing into things. It eventually comes across Legolas, who is shooting on top of a tower. The troll begins smashing the tower, until Legolas drops onto its head, sword in hand, mortally wounding it. The creature then smashes into the tower head-on, falling over the edge into a chasm below, killing it.
The individual chasing the war cart driven by Balin and others in the Extended Edition greatly resembles Peter Jackson's King Kong in 2005 in facial structure, behavior, and roar.
In the concept art book (Chronicles: the battle of the five armies edition) the concept art for these war trolls was going to originally have many of them with huge horns and spiny protrusions coming from their backs. An unused troll concept was the "Caber Troll" which was going to be a type of horned troll that would throw giant Cabers (logs/trees) adorned with spikes and hammers into the allied army lines. It is unknown why this type of troll was never used in the final film.