My Charlie sounds very similar to some of the descriptions above - it's challenging to find things he will even pay a little attention to while in his cage, but he is SUCH a playful handful when out of his cage (he gets into everything, loves playing with toys, etc.). So I make sure he gets lots and lots of out of cage time, and if I do discover something he's played with while in his cage, I stock up! (And it greatly varies - things he loves playing with while outside his cage will often be ignored in the cage, for example).
One of the wonderful greys at the rescue where I volunteer also loves toys but ignores a lot of them while in her cage, but I've had some success with attaching a small basket inside her cage and filling it with plastic foot toys that she likes and enjoys rooting through while in her cage.
And if there's a treat she loves,
@Sweet Louise - a clear acrylic/plastic foraging toy with the treat inside (so she can easily see it), may encourage her to play/forage a bit.