I broke the no waving to a scooter rule once but I felt it was justified.
40 year old guy wearing grimy coveralls on a rural highway riding a Honda Ruckus 50cc. As he approached he gave me a full armed wave and I couldn't help but wave back as I laughed my a** off.
And I've found with Harley riders you are allowed to wave provided they have waved first
These were a couple of one that got a chuckle outta me...
"right up until you get kissed by an amorous semi, or wise up and sell the bike to invest in a safer, more practical mode of transportation. Heroin, for example."
"If you do catch yourself mid-wave to a Vespa, however, it is acceptable to slowly turn it into an upraised middle finger."
"In fact, as you get better at riding, you'll become more and more functionally retarded."
Unfortunately, this last one has begun to plague me a bit. I feel real comfortable on my bike now after over 2 years commuting on it, zipping in and out of traffic. The bad part is, I keep catching myself riding a little more aggressively then I should be. Every morning, I tell myself to take it a little easier.
Just had a spider this morning on my way to work and I do find myself waving to scooters all the time...never slowly turn the wave into a middle finger though.