I am sure you all upload emails containing attachtments all the time. You surely would hate selecting the location of the file using the browse option. Fear no more, Firefox finally has a hand y addon called DragDropUpload that allows to drag and drop files while uploading stuff.
As a special case, the addon also handles single and multiple attachments for Gmail. Just drag and drop your selection to the Attach a file link in the gmail compose screen and you are good to go. The screen capture below shows how it works.
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