Oh, definitely try flyball! GSDs are very under-represented in the sport. There's only one other in the entire region, which covers the state of California, and it's in the Southern part of the state so, usually Halo is the only GSD at the tournaments we've been in.
Halo works hard, plays hard, and sleeps hard.
She has an excellent off switch, which is very important. At flyball practice and tournaments she's the only dog in our club that's in a soft crate, and she lays there calmly without a peep until we get on the field or in the ring. Then she screams like a chimpanzee!!!
She's also somehow managed to change the "no dogs on the couch" rule that was in effect for over 20 years, lol.