I have noticed an odd fact...dogs that I raise from puppies (Yukon and Bella) are not obsessed with anything, they like their toys just fine, but don't 'need' them.
Dogs that I adopt full grown (Alice and Titan) are COMPLETELY obsessed with balls. Alice loves soccer balls, basketballs, etc. Titan has a thing for tennis balls and this little red ball in particular.
This is Titan catching the ball after I kicked it.
Here he is barking, barking, barking at me to kick it again....he LOVES that stupid ball.