+4 Competence bonus to Perform: Comedy (everybody seems to think it's so funny).
+4 to saves vs. Fear and the DC to use Intimidate or Diplomacy on you (you're so dang stubborn).
Drawback: Can't use any magic items less than 10 years old, the hat requires you to stick to traditional, old-style magic items.
Or it could be an intelligent item, with a Special Purpose of destroying some obscure dice-rolling game that the characters have probably never heard of.