Marth

The Falchion is Marth's sword. It remains his only weapon through his two appearances in the Smash Bros. series, and was Fire Emblem's "icon" for both Melee and Brawl. With the exception of grabs and throws, Marth can only use the Falchion in battle.

In the games, the Falchion appears to be a golden broadsword during in-game battle sequences. However, its has been shown as a longsword with a steadily widening blade in its official artwork. The Falchion's design has been implemented in several other swords main characters use in Fire Emblem. Of note is in Fire Emblem, Marth needs the Fire Emblem shield to wield it. This requirement isn't upheld in Smash Bros.

The Falchion has a property no other weapon has: attacks are stronger if landed at the tip of the blade. Successful use of this is the crux of Marth's success.

Trivia

 * Marth's sword Falchion is not actually a falchion. His sword is a one-handed sword.