Ooo! I remember...
-We had two couches in our basement that had these awesome cushions that you could prop up really easily. I would go to one couch, take off the cushions on both couches (one couch was considerably bigger than the other, thus more cushions), and prop all of the cushions on the smaller couch. I would first make walls out of them, struggling to keep them in balance, and I would leave a crack open for my "door". Then I'd make the roof out of these large square cushions, but most of the time I'd use blankets and drape it across. Then I'd drag pillows into my fortress, and some beanie babies. I'd pretend I was a cougar if, say, the beanie baby was a cougar. It would be my cub or something like that. And I would always pop in a movie and watch it through my "door". I enjoyed myself a lot that way.
- I would go into my backyard with some friends and take out pinecones. We'd make "nests" for the pinecones and sit on them, pretending they were our eggs. If you broke them (which was nearly every time), you failed as a mother. xD
-I'd go to my pool and my friends would pretend to be certain "Pokemon", and we'd attack each other with the water.