Thinking Putty
Now I know there is a technical name for a material displaying these properties, but I can't remember it.
Any ideas.

It looks and sounds just like Silly Putty.

According to Wikipedia, it is made of a silicone plastic (Source : Silly Putty - Wikipedia, the free encyclopedia)

I hope that's what you were wanting to know. :p

**EDIT** - It also says its an inorganic polymer, which is why it is able to bounce and stretch.

It's viscoelastic or thixotropic. Which are types of non-Newtonian flow.

But the material is just plain "plastic" :P