Is it possible to remove the tap effect on an item inside a gridview?
Yes, you need to modify the GridViewItem style in the ItemContainerStyle property.
Note that the default style of system controls changes between versions of the OS. The Windows 10 expanded (note that the platform renders the items with simplified visual tree by default to improve performance) style of the GridViewItem can be found in "c:\Program Files (x86)\Windows Kits\10\DesignTime\CommonConfiguration\Neutral\UAP\10.0.10240.0\Generic\themeresources.xaml" (or some such place in the themeresources.xaml file) by searching for TargetType="GridViewItem".