Don't smile and wave. That only works for road rage.
If they're heckling you, they'll be happy with any reaction they get. Anything you do will make you look like a dork, and they'll get satisfaction from it.
If it's just heckling, it's best to totally and completely ignore them. That's when they'll see that you're not playing along and yelling back or cowering or whatever they were expecting from you.
Giant Innova (1992) What a Rocket Metallic Ice White
I don't yell back I make tracks. I have been commuting for 5 months now only average 200 miles a month to and from work but I ride in traffic. Had a dude getting really rude with me for a few months (paths always crossed at the Highway exit) after seeing me for few months everyday he went out of his way to apologize and give props for the work he got to watch. In the rain , in the heat or cold he saw me grinding it out . I can appreciate what it takes to change and it shows me that some people out there re truly willing .......