Which planet in our solar system has the shortest day?

Space is wild when you really think about it. We're sitting here on this rock that's perfectly suited for us, surrounded by planets that look like they were designed by a kid with a crayon box and zero regard for physics. While we're comfortable with how things work on Earth, including our nice predictable 24-hour days, every planet out there has its own bizarre routine. Can you guess which planet has the shortest day?