Eldar

"Eldar" is a word from the Tolkienverse which refers to a large portion (but very importantly, not all) of the elves living in Middle-earth and Valinor. The critical difference is that the Eldar were elves who accepted the summons of the Valar and came to Valinor - those who did not are called the Avari and have been referred to as "wild" and "less wise" than the Eldar.

The "Eldar" are also a species in Warhammer 40,000, though aside from the name and elf-like nature (although managing to create a god of hedonism through milennia of nonstop orgies probably doesn't qualify as elf-like)  these Eldar have nothing in common with their Tolkienverse counterparts.