Are there dark elves or lone elf warriors in LOTR?

Question

In the books, an orc in the tower of Cirith Ungol (after the Battle of Cirith Ungol) runs into Samwise while he's wearing The Ring. The orc, Snaga, thinks it's a "Great Elf-Warrior" but it's only Sam. In the movies, one of the orcs hears Sam trying to psych himself up while grunting and supposes the source is a "dark elf."

So are there references to dark elves or lone, elf warriors running around Middle Earth just killing orcs and goblins?
[By lone, I mean an elf not directly and currently affiliated with any of the elf cities.]

Answer 1

I think that depends on how the question is meant.

There certainly were not Elves just wandering around Mordor in the late Third Age. There are not all that many Elves left by this point, and they are mostly limited to a few areas. It is worth noting that he actually says "one of those bloody-handed Elves, or one of the filthy tarks" - tark means a Gondorian, which is much more likely enemy to encounter in Mordor.

See this question: Who are the tarks and what power do they have regarding the Watchers?

However, there are cases of Elves wandering in the wilderness and fighting Orcs, but they had some affiliation with a city or group of elves -- such as those who guarded the borders of Nargothrond (Silmarillion Chapter 21, Of Turin Turambar, says Turin "had no liking for their manner of warfare, of ambush and stealth and secret arrow".)

Beleg wandered around the woods a lot seeking Turin, but he picked up Gwindor of Nargothrond before he actually attacked the Orcs holding Turin -- however earlier it is said that he sought Turin "among many perils" so he probably fought Orcs during that time. But Beleg served King Thingol.

The Green-Elves of Ossiriand did live secretly in the woods, refusing to go to battle, after the death of their leader Denethor [not the one in LOTR]. It's likely that they killed occasional Orcs who wandered into their area by stealth.

Answer 2

I'm not sure in LOTR but in The Silmarillion, there was Eöl "The Dark Elf" (Silmarillion page 153) who was a kinsman of Thingol but became restless, eventually living apart from the other elves by dwelling in Nan Elmoth. He was unusually known to have befriended the dwarves and known to have hated the Noldor. He was also a very skilled craftsman and made the swords Anguirel and Anglachel, along with Armour (that he devised out of black metal) called Galvorn.

He's a pretty controversial but very interesting character.

References include The Silmarillion chapter "Of Maeglin"; Morgoth's Ring, The War of the Jewels and The Peoples of Middle-earth (i.e. History of Middle-earth parts 10–12), etc

Come to think of it in LOTR there was Glorfindel who was looking for Frodo and did not fear the Ringwraiths and they rode off in the opposite direction just even at the sight of him. At this point, he had powers almost equivalent to a Maia but did not openly show it. LOTR pages 204-205.

To add to that the goblins in The hobbit feared the swords Orcrist and Glamdring, both originally owned by king Turgon and a lord of Gondolin (estimated to have been Ecthelion), also note Orcrist is Sindarin for "Goblin-cleaver". So there must have been at least two noteworthy fearsome elves. The Lord of the Rings: A Reader's Companion, p. 265. The Hobbit, "Over Hill and Under Hill"

Answer 3

Elrond's twin sons - Elladan and Elrohir, often went out together orc hunting to avenge their mother Celebrian who was captured by Orcs and tortured.

"But her brothers, Elladan and Elrohir, were out upon errantry: for they rode often far afield with the Rangers of the North, forgetting never their mother's torment in the dens of the orcs."