It's made by Cricut and they call it a Spatula Tool. It has a very thin front edge that is good for getting under prints and then it tapers up a little bit to make it stronger.
I slide it in under a corner and work it around the print and then lift up a bit and the print pops off. It looks like the spatula we have is an old model but I did a search on E-bay and there are a several of them for sale for less than $10 bucks. Just search for 'Cricut Spatula Tool' and look for one with a green handle. Cricut's has a new spatula design but is a little smaller and I don't know if it works as well. I might buy one just to try it out.