The Excalibur can be swung while walking backwards, which is useful for knocking back enemies during retreat.
Unmodified Excalibur sells for slightly less than the Hallowed Bars required to make it (460 vs. 480), but since the random modifiers increase a melee weapon price by 11.2% on average, crafting and selling Excaliburs in bulk is still about 6.6% more profitable.
A better option is to craft several Excaliburs, sell the good ones as-is, and upgrade the worse ones into True Excaliburs (which is a good use of surplus Broken Hero Swords, as noted on their page).Verify
Prior to patch 1.2, the Excalibur was the strongest sword in the game.
Excalibur is the mythical sword of King Arthur from Arthurian legends. While some sources conflate Excalibur with the "Sword In The Stone" by which Arthur proved his kingship, more reliable sources have them as two separate swords. (Excalibur is later given to Arthur by the Lady In The Lake.) In Terraria, the Sword In The Stone is separately represented by the Enchanted Sword item.