Pepper (y'know short dark hair, horned glasses) from 1960's Josie and the Pussycats - replaced by Valerie

Guy with mustache from Garfield - showed up in a 10th anniversary strip

Pigpen and a couple of Charlie Brown's friends from the 50's

Gwen Stacy's twin children with Norman Osborn - written out due to the negative reaction to this story. They didn't show during Dark Reign, Goblin nation or the Osborn series and are unlikely to ever show up again.

Young Justice supporting characters : Arrowette and her mum , Empress, Traya (correct me if I'm wrong)


Others?