There are many items I enjoy a lot like Mille Marteaux, Sacred Bow, Great Fairy Sword...
Though if I had to choose the funniest, I'd say Tension/Morolian Blaster
Not only they have a cool skin with the purpre circle bullets, but they are the only weapons in the game that have different (and funny) sounds for normal/hard/special attacks and when you hit an enemy with the special.
*Bzz! Hey! Chu!*