With 13 piggies it gets a bit expensive to cater for all their entertainment needs so I tend to recycle cardboard boxes, empty loo rolls, primark bags. I rob my mum's apple trees for twigs which they really love playing with.
My piggies are not really that fussy, but get hours of fun out of demolishing a Magners box.
I've tried buying all the toys but they're only interested in something they can destroy, or alternatively eat, and I get a bit upset when I pay £5 for a willow ball stuffed with hay and it lasts all of 20 minutes.
The one thing all my piggies like is a foldaway tunnel and they have hours of fun hiding from each other in it.