I have never met a cat that doesn't like to play. Even the old, arthritic ones I've known can muster the energy to bat at their toy of choice.
What toys do your cats love? What things do they turn into toys?
My youngest goes absolutely insane over long grass. We have a hay field, so certain times of year, there's an entire field of toys. Individual blades are not that exciting in situ, but once removed and waved in the air, or dragged along the ground... woo hoo! Excitement!