Build a two story cardboard box castle/hut for your cat! Everyone knows you don't need to buy them toys because they will play with just about anything! This thing doubles up as a play area and a place where your cat can sleep. As a bonus your cat will like being up high. I set myself a challenge for this project to use the least amount of sticky tape as possible.
Step 1: Materials and stuff
Sticky tape (Not much was actually needed)
Cardboard boxes (Same size helps)
You don't really need all of these items as it's not going to blow up if you make it a different way. You might as well experiment a bit!