Boxes are the ULTIMATE toy for my kitties! The box my SS presents came in 2 years ago sat in the dining room until this past Christmas because it became Harley's "bed". I tried to get rid of it before that but he raised such a fuss I was constantly bringing it back up from the basement burn pile and giving it back. I guess by the time Christmas came around again there was enough new stuff to play with (tree, ornaments, etc) that I was finally allowed to get rid of it.
The best toy I ever had I made on a whim. I took a small box, cut holes in the sides big enough for them to get their legs through and look through but not big enough for them to crawl through, and hung one of those jingly balls from the center. They went CRAZY trying to get that stupid ball! It would occupy my one cat for hours.
Yep, sometimes the best toys are the simple ones.