This is another unknown plant. This hosta, grown in deep shade, has very dark, almost black edges.
Could be Hosta 'June', but there are so many hosta. Try posting on Gardenweb's Hosta forum if my suggestion doesn't look quite right.
Here is a link that might be useful: H. 'June' images
I think carrieb is right. Here is my 'June' to compare. She gets a little sun in the afternoon:
You found a winner in your garden. Hosta 'June' is one of the most striking plants.