Not really a bus "ride", but it's the most fun I've had on a bus.
This summer, at DCI Championships, we spent a solid 2 hours of semifinals night, not at the stadium, but in the bus. We had one guy on the outside luring people (mostly members of the Blue Stars) to walk past our bus, and whenever they did, 5 of us would pop open the window and scream at the top of our lungs. The reactions of some were utterly priceless.