Without a doubt, the most frivolous item with a permanent place in my one-butt kitchen is a Watermelon Keg Tapping Kit. I use it to serve watermelon martinis, which are equal parts vanilla vodka, Watermelon Pucker Liqueur, and fresh watermelon juice.
The Watermelon Keg Tapping Kit can be purchased on Amazon.com. (Disclosure: This is an affiliate link. If you click through and make a purchase, I will earn a small commission, at no additional cost to you.)