From MERP (specifically from Treasures of Middle-Earth); Sulhelka (the Sword of Celebrimbor) has the power to freeze 10,000 cubic feet of water, create an area 100 feet wide of utter cold and can instantly appear in the wielders hand from up to 100 miles away. The Uttercold can be used three times a day.
The Staff of Lore can summon one storm, hurricane or tornado per day, or cast any spell from Plant Mastery (up to the 10th level), while the Staff of the Serpent allows the wielder to transform into a serpent once a day.
Voronwe is a telepathic mithril sword which can detect evil within 50 feet, and automatically leaping to its owners hand without being drawn; if that's not impressive enough, it can also teleport the wielder and one other companion up to 100 miles away up to 3 or 4 times.
The Doorway necklace can teleport its wearer up to 3 miles once a day (and was found at the shrine of Sholgic the ghost-god, a being whom I understand is a disguise of Sauron). The Dark Spectacles allow one to see through 2 feet of stone or wood. The Daen Star-Compass can redirect any projectile when facing North, and redirect any arrow back at its archer when facing South.
The Listening Helm grants the wearer the ability to use sonar.
Rimalagon allows the wearer to transform into one of four birds once a day (a sparrow, a crow, a small hawk or an eagle). Also as noted under the Robes of Aman, Gandalf the White was almost beyond harm in his new incarnation.
Wielding Ringil, Fingolfin was able to dodge most of Morgoth's earthshaking attacks, and strike him seven times. Sauron's javelin will seek out its target to 9 miles, before teleporting back to the thrower.
The Spears of Following follow the target up to 200 feet. Spinerunner can transform between a dagger and a two handed sword. Stinging Tongue is a composite blow gun designed by Khamul the Rignwraith before he vanished into the Shadow World after his masters final defeat.