I have 2 puppies (4 & 5 months old right now) but I also had a GSD that was 10 when he passed away in October. I have tons of softballs, kongs, and baseballs. The only bad thing about baseballs is that they absolutely love the sound they make when dropped on the foyer floor....I don't so much. LOL
For outside we have a regulation basketballs, soccer balls and some large rubber balls (like kids use in elementary school). We also have a soccer ball with a bell in it - it's absolutely great, especially for older dogs that have vision problems, as they can learn to still play ball from following the sound.