Great Pumpkin Top Hat

Nobody buys the Great Pumpkin Top Hat; you take it off a boss. It is a possible drop from The Great Pumpkin, the Level 3000 raid boss with 415,000 HP, who is reached through a portal the Witch opens. The wiki gives no drop rate, only that the hat is a chance reward next to regular drops such as Candy Corn and the Pumpkin King title.

The buffs are modest and fruit-oriented: +7% Fruit Damage, +10% Fruit Damage Resistance and +250 Health. Set that beside the Coral Crown, with +10% Fruit Damage and 500 Health, or the Mummy Headdress, with +5% Fruit Damage and 250 Energy. The Top Hat is the only one of the three that pairs an attack bonus with a fruit-specific defense stat.

It is a Mythical accessory that works in all three seas, listed under Update 30.1 by the wiki. The in-game blurb calls it a mysterious hat once worn by a sinister jack-o'-lantern, with an eerie presence still lingering inside.