Quickling
The Quickling is a small fey possessed of super-speed hailing from Dungeons & Dragons. Although originally considered a member of the brownie family, the quickling has no mythological precedents and has done a far better job of surviving the changing editions than its peaceful cousins. The first version of the quickling appeared in the Monster Manual II for Advanced Dungeons & Dragons 1st edition. Native to the Greyhawk setting, the quicklings were originally brownies, but were corrupted by dark magics into a murderous predatory race of fey. This version of the quickling was updated in the Monstrous Compendium Annual 2 to suit the 2nd edition of AD&D.
The defining trait of quicklings is their superhuman speed, which makes them incredibly hard to fight; they have insanely high defenses to represent just how hard they are to hit, and can usually slash you up pretty badly in return.
Check out this handy link for an in-depth examination of quicklings throughout the ages of D&D: http://www.enworld.org/forum/showthread.php?592544-Monster-ENCyclopedia-Quickling