Oh, a smile and a *nod* is generally my style, especially at an intersection! Maybe if the road's clear and I'm coasting steadily, I'll wave - and I've got a few (thousand) miles under my chamois. \
Couple years ago, two friends and I decided to Try The Thursday Ride together (a faster ride for all of us). If there are three of us, we haven't been dropped - we've formed our own group, right?
So, off we go... and coasting, almost to a stop, at the first intersection, my buddy sees a buddy driving by. He waves, she waves... and and wobbles and she DOES fall down... SPLAT! Nothing hurt but her pride... she'd even been telling him that she had surprised herself at how good a cyclist she was...