Anything that is not too heavy or tied down to the floor! They've even dragged my dad's tie around as a toy and several of my socks (I'm still missing some) and even one of my shirts!
And litter from the litter box O_O Echo will scoop a bit in her paw, fling it and chase after, then, once realizing it's too small for her to effectively bat around, she'll get a bit more, fling, and realize it's too small again!