Quick scan, not saying any are great - you need to eval
Ecommerce Theme 1 : Premium WordPress Themes, Business WordPress Themes, WordPress CMS Themes
Demo made with the one above:
Ecommerce Themes Demo (Pretty nice looking)
Themes » Art Commerce Theme
WPDesigner » Market WordPress Theme
I just searched Google for store product wordpress theme and those are a couple of the top listed ones that looked good. There are lots more.
Oh and here's another that looks interesting
The Market Theme - Ecommerce is now simplified
Hope this helps and best of luck!