Meowmere

Meowmere is a secret sword weapon obtained by placing a Far Away Stone on the plant pedestal in the basement of the Wizard's Tower. It is based on the weapon of the same name in Terraria. When enemies are slain with Meowmere, or with a weapon forged to have its appearance, they explode into rainbow sparkles.

In Stardew Valley, Meowmere is notable for being the only sword that deals exactly the same amount of attack damage with every swing. Despite being the sword with the highest base damage in its origin game, it is outclassed in Stardew Valley by any weapon above level four, such as the Templar's Blade and Bone Sword.