Sugru is probably one of the most universal household items, ever. In this video from Dave Hax, demonstrating just how amazing the self-setting silicone rubber is around the house. It can be used to mold wires, seal leaky shoes, and create a hook for storage as well as countless other things.
Sugru is basically a glue that turns into rubber, but feels just like play-dough. It can bond to almost any other material and cures just by exposing it to air. This incredible stuff will even stay bonded during extreme heat and cold.
Stick tennis balls to it and make custom shoe racks