I'm a project maintainer, and we use the ticketing system for bug reporting. It's common for patches to be attached to ticket. In the previous bug reporting tool used by SF, when a user attached a patch, there was a "patch" check box (IIRC). If this box was checked when attaching the patch, then subsequent clicks on the URL for the patch attachment would result in opening the patch in the user's browser. But with the current SF ticketing system, when I click on an attachment link in a ticket, the only choice I have is "Save file".
A general purpose MIME type identifier for attachments would be even more helpful. This would allow the browser the opportunity to select an appropriate viewer for any type of attachment.