I have one of these and while my dog will occasionally try to chew/lick it when she gets frustrated, it's made of smooth hard plastic so she's not actually able to destroy it or get a good grip on it. I wouldn't use it if you have hardwood floors, though - I assume if it was dropped on a hard floor, it might eventually break.

I have the IQ Ball, Dog Twister, and the Kong Wobbler. After you teach your dog how the toys works, he'll most likely "solve" them at their hardest settings in about 5-8 minutes. But my dog still gets all of her food through puzzle toys.

Frozen kongs filled with wet dog food are great though. They'll keep my dog busy for about 30 minutes.

I use a treat ball from Amazon that allows my GSD to work for treats but also distracts her when I leave. It takes her quite a bit of time to get them out, which makes her tired. We also use it for rainy days when she can’t go run dog treat ball

Edit: frozen peanut butter in a Kong also works for a bit

Coconut's been messing around with this one:

http://www.amazon.com/gp/product/B003ARUKTG/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

and this one:

http://www.amazon.com/gp/product/B003DQJQ1C/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

But she likes to take the wood pegs from the latter one and run off with them so I'm worried she's going to choke on them. She only gets to play with that one under supervision.

But now I'm thinking of getting some timber from Home Depot for her to gnaw on.