Originally Posted by Tinton

I'm a vehement acknowledger. Waving is great, if you don't have to do it frequently. Subtle movements can be just as polite. Not the "I'm so awesome--have an imperceptible head nod" crap, but at least a hand, or nod, and sometimes even a smile.

It's rude, bad form, and generally jerk-like, but I once exacted revenge on an "ignorer."
I was riding my dad's old Gianna Motta with downtube shifters and 1980s components. I saw a 20-something on a Cannondale with clip-on aerobars across from me at an intersection on a popular cycling road. We waited a few seconds for traffic, I looked his way, and offered a quick wave. He ignored me and continued to look straight ahead.

We headed in our opposite directions, and I ruminated on his rudeness and my boredom. I decided to chase him down and pass him. I turned around about two minutes later, and started the chase.
I was zooming his direction at around 25 mph. When he came into sight, he was about 3/4s of a mile ahead, pumping along smugly on the aerobars (that jerk!)
We were both on a straight flat when I caught him. I came up behind him, and hovered around 100 feet back for a bit. The dude was moving at about 20 miles per hour as I started to speed up to pass. I rested my forearms across the bar tops, and pumped in 54x13 (old campagnolo chainrings.) I was coming up behind him at about 28 mph, and when I moved over to the centerline to pass him, I was going 32 mph. I casually looked over for a few pedal strokes, and then continued on my speedy way.