Flying Pig Cincinnati for sure. Extremely well run and organized.
My favorite quirks from years past:
1. Singing Elvis in the middle of the street giving people high fives at the top of the hill!
2. Full Chorus on risers singing on the main lookout over the river.
3. High school football team water stop. The flying pig organizers used to do (or still do) a poll for best volunteer run water stop to win some fundraising money? The high school football team took it seriously and treated it like a football practice. Yelling, screaming words of encouragement to the runners. Shirts off, super pumped up high school kids acting over the top. They got my vote that year. It was cool to see.
4. Fireworks at the start.
The only bad part is it is a challenging course. Miles 5-8 are uphill. I don't believe they give prize money for professionals, so all of the funding and effort is put into the race day experience for the regular runners.