Well Mitzy's all time favorite is fetch and she will play for hours
But we also play "hide and seek". I first make her sit & stay in say the living room, then I will take a toy and go hide it somewhere in the house. When I return from hiding it she will take off and go try and find it. Sometimes she needs a little help but most of the spots I try to make easy to find for her

She loves this and I think its a great way to keep them stimulated