Flexible metal putty knife
If you're an avid watcher of Debi's videos then you have probably seen the one where she puts paint in the freezer to thicken it up. She uses a number of tools in that video to create a funky layered paint effect, including a putty knife similar to this one. This one is made of flexible stainless steel with a plastic handle for a longer life in your tool arsenal.
It measures roughly 7.5" long and is 1.25" wide.
You can watch Debi's video here on YouTube