Tiara

Tiaras are part of any Sailor Senshi's fuku, except Sailor Cosmos, Sailor Galaxia, and Eternal Sailor Moon.

Sailor Moon's tiara served as her first weapon. In the manga and Crystal, Sailor Moon used her tiara for two main attacks; Moon Frisbee and Moon Twilight Flash. The latter was one of Sailor Moon's manga only attacks and was first used in Volume 01, Act 04. A bright light flashes from the gem on her tiara. She received upgrades to her tiara during the Dark Kingdom arc of the manga and Crystal, but in every other manga and Crystal arc it stayed the same.

Sailor Moon's first tiara was given to her when she first transformed into her regular Sailor form as Sailor Moon.

When looking at the tiara from a distance it appears to have a rather simple smooth golden design with a circular red gem at it's centre. On closer inspection though one can see that it in fact has subtle details engraved in its surface and the gem itself is encased in a golden frame.

When removed from Sailor Moon's forehead and activated for her Moon Frisbee attack (renamed Moon Tiara Boomerang for the manga re-release) the tiara morphs into a flat circular shape with the gem placed on top.

An interesting subtle feature in this form is the small chain with a small crescent moon shape attached to one side. This appears to serve no function though is a nice unappreciated detail.

The tiara was destroyed during the battle with Jadeite in Act 3 of the manga when Sailor Moon threw the tiara at him and Luna simultaneously pushed a key on Mercury's computer causing it to wrap around him. Sailor Mars then attacked Jadeite with her Akuryo Taisan, destroying both him and the tiara.

In the anime it can be removed in order to perform the attack, "Moon Tiara Action," (Moon Tiara Magic in the old English dub) in which she throws the tiara like a frisbee at her opponent. It is also used in the one-time attack, "Moon Tiara Stardust," in which it sprinkles healing moondust over possessed children in the fifth episode.

In Pretty Guardian Sailor Moon, the second attack Sailor Moon gains is ''Moon Tiara Boomerang. ''

Dark Mercury had tribal designs on her tiara. Sailor Jupiter had an antenna which she used like a lightning rod.

Trivia

 * The colors of the gem on the tiaras are based on the Senshi's signature color, except for Sailor Saturn whose tiara gem was white in the manga and original anime, while her signature color was purple.
 * Sailor Moon is the only one whose tiara changed in the original anime.
 * During the Dark Kingdom arc of the manga/Crystal, Sailor Moon's tiara is destroyed in Act 3 after the fight with Jaedite, but is soon replaced by a more ornate one in Act 4, then becoming crescent shaped when Sailor Venus appeared and claimed to be the princess. This was most likely foreshadowing her identity as Princess Serenity.
 * When the nine Super Sailor Senshi evolved into their Eternal Sailor forms, the gems in their tiaras became stars, except for Eternal Sailor Moon who had no tiara at all, but a crescent moon.
 * Sailor Moon and Sailor Jupiter were the only Guardians whose tiaras could be used in attacks.

Gallery
Diadem Tiara