Kongs, that is!
I've just been sat watching my two with theirs and it's funny how different they are! The oldest (always believed to be the more intelligent one) chased it around the floor licking frantically at the opening to get stuff out (had to retrieve it from under the sofa twice). But I was in awe at the puppy - she just stood in one place and repeatedly picked it up and bounced it off the floor so everything fell out! Clever wee sod
They normally only get them as we're going out, so I've never seen them do it before, it's quite funny! Reminded me of the cream egg adverts