Myrtenaster

Myrtenaster (Mur-ten-es-stur) is Weiss Schnee's weapon of choice. It is a Multi Action Dust Rapier (MADR) that seems to act as a focus or source for Weiss' power.

Description
Myrtenaster is standard-sized for a rapier and primarily gray in color. The hilt forms four prongs that act as a guard around the revolver's chamber-like mechanism in place of the usual basket hilt. Weiss controls this mechanism with her hands, and can change the modes freely. There are six modes in total, all of which affects Myrtenaster's combat abilities. They are Red, Light Blue, Violet, White, Yellow, Blue. Each mode also seems to have another setting where runes of that color appear on the blade, but only white and red have been seen doing this so far.

Myrtenaster is highly durable, slashing away at the Giant Armor with no visible side effects to the blade. Its most prominent ability lies in the revolver-like mechanism held within the hilt, which is color coded with various attributes activating depending on the mode.

Additionally, Episode 8 revealed another mode with a color-changing circle (turning from light blue, to black, then red, and returning to light blue), with alternate effects according to the color. It is unknown if this 'mode' is merely another use of an already-known mode, as it may possibly be the blue mode due to the color-changing property and the repulsion effect.

It appears that red is a repulsive effect (harmonising with the shielding/attack blocking effect seen in the White Trailer); the light blue appears to be an attractive effect, also seen by how it allows Ruby to scale a cliff-face as if she were running along a horizontal surface. White (used for Air Step) is a force disc that acts like a solid platform and black appears to be a stasis effect that prevents stored energy from being released.

Excluding the revolving hilt feature, while Myrtenaster does have some ranged abilities it does not, contrary to all other protagonists' weapons so far, seem to have any classic "gun" abilities.

Trivia

 * In keeping with the combination of guns and melee weapons demonstrated with Ruby's High Caliber Sniper Scythe, Crescent Rose, and Blake's Gambol Shroud, some fans have called this weapon type a "Revolver Rapier".
 * According to early concept art of Weiss and her weapon, it seems that Myrtenaster did not have a basket hilt, but instead possessed a classic gun shape with the barrel lengthening into the blade and a magazine or grip behind where the Dust was supposedly loaded.
 * Myrtenaster (Myrten Aster) is German for a family of flowers (Myrtle) that are typically found to be white, but can come in a variety of other colors.
 * Unlike many common rapiers, Myrtenaster does not have a knuckle guard, possibly due to the basket hilt. It also does not have a particularly heavy pommel either.
 * Myrtenaster seems to be lightly based off of Squall Leonhart's signature Revolver gunblade, from Final Fantasy VIII, with the revolver hilt.
 * Myrtenaster can be seen simultaneously as the most static and dynamic of all the weapons in RWBY. Despite Weiss' rapier never changing its physical form, it does have six different Dust compartments that give it multiple abilities and make it quite adaptable to any situation.
 * Whenever Weiss charges with her weapon, a loud pitching screech can be heard.