Unicorns

Unicorn ponies, or sometimes simply unicorns, are one of three types of ponies living in Equestria, characterized by their horns and their ability to perform magic.

Traits
As the name suggests, all unicorns have a long horn protruding from their forehead, which glows when their magical powers are used. Generally, unicorns are not as strong or durable as earth ponies. Despite being associated with their magic, a unicorn's horn is strong and sharp enough to have mundane uses. One unicorn (nicknamed "Pokey Pierce" by the fandom) used it to pop balloons in Call of the Cutie, and Twilight Sparkle has used it to charge an opponent on several occasions. Twilight Sparkle and Rarity have been seen using their intellects to compensate for their dearth of physical talent, as when Twilight earned fifth place in the Running of the Leaves in Fall Weather Friends and Rarity overcame her captors in A Dog and Pony Show.

Unicorn magic

 * See also: Magical traits 

No other pony race has been explicitly shown to perform magic, making unicorns unique in their ability to conciously utilize it. The most common manifestation of unicorn magic is manipulating objects ethereally, aka telekinesis. Rarity makes her dresses and builds birds' nests using telekinesis, and Twilight utilizes it extensively in many activities. Some unicorns are also capable of controlling multiple objects at the same time, most notably Twilight and Trixie.

Unicorn magic requires concentration and effort, as Twilight explains to Spike at the beginning of Feeling Pinkie Keen and to the Cutie Mark Crusaders in Call of the Cutie. When she levitates the Ursa Minor during Boast Busters, she visibly exerts herself, gritting her teeth and tensing her muscles.

Unicorn ponies are capable of learning other spells, which are normally based around their special talents represented by their cutie marks or learned from spellbooks. For instance, Rarity possesses the ability to detect gemstones (A Dog and Pony Show) and can create light displays and complex illusions (Suited for Success).

Spike claims Twilight can do at least 25 things with her magic during Boast Busters, and she has since been confirmed to have learned Rarity's gem-finding spell in A Dog and Pony Show, as well as a few others, such as a temporary wing spell, a spell allowing non-pegasi to walk on clouds (Sonic Rainboom), or a spell to transform rocks and sticks into formal attire (Feeling Pinkie Keen). She is also capable of teleportation, or "winking out" (which she occasionally does compulsively, as indicated in the third episode of season one). This often leaves her briefly disorientated afterwards and once left Spike slightly singed when she teleported him with her in The Ticket Master.

Trixie also possesses several unusual and flashy magical abilities that help her on stage (whether or not she posseses any magic outside of the theatre is another story). During Boast Busters, she took control of a rainbow made by Rainbow Dash and created a whirlwind from it. She can also create storm clouds and produce a small flash of lightning from them, as well as bind ponies and other similarly-sized creatures using rope.

Appearances
Canterlot appears to be a city predominantly populated by unicorns, with notable exceptions being Hoity Toity and Princess Celestia's pegasus pony guards, as well as Celestia and Princess Luna themselves, who are alicorns. Ponyville has its share of unicorns, but unicorns are only seen as waiters in Applejack's visit to Manehattan. Since they, along with earth ponies, lack the natural ability to walk on clouds, they are not ordinarily present in Cloudsdale.