Cave Trolls are extremely large humanoid monsters based on the trolls of myth as well as ogres, they appear in Lord Of The Rings as minor antagonists - both in the book and film series.
In the book version of The Fellowship of the Ring there are many cave-trolls. The first cave-troll is fought by Frodo who stabbed its foot, but the troll is not killed. The trolls are described as having long arms, dark green scales and toe-less feet. Soon, two more cave trolls throw two large boulders to form a bridge so the Balrog could pass.
In the Peter Jackson's 2001 movie version, there is one cave-troll which is killed by the Fellowship members who spear and hack at the cave-troll with no avail until Legolas dispatches it with an arrow. The arrow enters the roof of its mouth and goes straight through the troll's brain, emerging from the back of its head after becoming stuck in the troll's thick skull. In the movie made by Peter Jackson the cave troll is computer animated. Its movements were done by Randall William Cook, wearing a motion-capture suit. It also has a set of nostrils located higher than the space between its eyes, making its nose look almost like a "third eye".
In Ralph Bakshi's animated movie, the cave-troll has quite an inconsequential part. Gandalf says "Orcs and something else! A great cave-troll I think!" when he sees the orcs through the east gate. Boromir then closes the gates but they are barged open by a large creature covered all in fur apart from it's hands and feet (Presumably the cave-troll). After this, Frodo leaps towards the creature, stabbing it through the foot, shouting "For the Shire!" as he does so, causing it to flee.