While Paul Pierce might no longer be a Celtic, he is still repping Boston in advertisements and tweeting them out to his fans. In this commercial for Dish he just posted, he teaches people how to talk like a Bostonian. Dish must have conceived the commercial spot before the Truth was traded, but at the end he says "a good reason to move to Brooklyn is the pizza."
Of course, Pierce wasn't the only athlete with Boston ties to do one of these promos. Current Patriots star Vince Wilfork also did one. Check that video out at PatriotsLife.