This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / The Lord of the Rings Online
The Nameless of Moria, the game's version of the "nameless things that gnaw the earth" Gandalf would not speak of further. He wasn't kidding.
The Abominations in the Dunbog and Isengard instances. Saruman has made Mutants in Middle-earth, and they are creepy-looking.
Some places of the game are designed to be Nightmare Fuel. Such places include (but are not limited to) the Barrow-downs, the Red Swamp, the Fields of Fornost, the northern half of the Trollshaws, Goblin-Town (due to the general feel of the place), most of Angmar (naturally), parts of Moria, Mirkwood, Fangorn, the Paths of the Dead, and so forth.
This troper was mildly disquieted when she took a closer observation at the Pillar of the White Handnote To describe: It is a pillar with a giant, stone-carved White Hand on the top. Though it gives off a certain image of a giant hand, cut off and impaled upon the pillar, and pointing toward Orthanc with blood-stained fingers.
Volume IV: Book 4: Chapter 12 is a constant stream of nightmare fuel both in- and out-of-universe. To wit: The Rohirrim do not arrive and Gandalf loses his battle with the Witch-King, forcing your character to flee and find Pippin. The lords of Gondor are slain, including Prince Imrahil. Gothmog captures you alive and brings you to the roof of the citadel to see Denethor's death. Pippin sees this happen, and Denethor commands the hobbit to flee with his last breath. Pippin runs for the edge of the city, but is snatched away by a fell-beast. Thankfully, Denethor reveals at the end that all of this has merely been a vision from the Palantír.