This gets into definitional territory as I'm quite sure that gruppos I consider to be classic would not be considered classic by many. My favorite group for the combination of aesthetics and function is the 8 and 9 sp Campy Record gruppos with alloy levers. They work extremely well, they're durable, repairable and beautiful. I think it's the prettiest crank design ever executed. I prefer the 9sp alloy, but for pure aesthetics hard to argue with the earlier 8sp Ergo with the c-record post and deltas.