Kid Chocolate. One of the first truly "modern" styled fighters. Great bobbing and weaving and countering abilities...plus his name is awesome. Oddly enough, Mike Tyson cited him as one of his major influences.
Barney Ross, greatness of all time, and the first man to hold 3 weight titles at the same time, 4 years before Armstrong repeated it.
Check-out Carlos Ortiz's ring savvy 'n poise dissecting 'n decimating Len Matthews with BLISTERING combos.
Tommy Loughran, his fights against walker and braddock are both on you tube. Tommy is a great fighter to watch, what boxing is all about hit and not be hit.
i wouldnt go as far to say classics but watch ike against byrd and tua. its always interesting to ask yourself if that man could have ruled the heavyweight division if he was sane.
His bout against Beau Jack is one of my all time favorites. Anyone going up in weight and defeating Kid gavilan is legendary.
If there's any of him on there, Pascual Perez. Possibly hardest Flyweight puncher ever. 4'11. Nuff said.
I know hes not an Old timer but one of the best Boxing displays ive seen was Jesse J Leija vs Azumah Nelson II Leija was in the ZONE that day. He beat Nelson very convincingly in that fight.
Carmen Basilio, if only to see some WICKED bodywork, and some serious examples of mind overcoming matter.