Technology blogger Amit Agarwal has posted the mysterious keyboard shortcut for deleting messages in Gmail:
If you are reading a message in Gmail, press the # key (Shift+3) and that message will instantly move to Trash. Alternatively, select one or more email messages in the Gmail list view, press the same # hash key and all the selected Gmail conversations will be deleted in one batch.
We’ve blogged about Gmail keyboard shortcuts before; add this to the list, definitely. Note: make sure you have Shortcuts enabled in your Settings before you try this, or it won’t work. — Wendy BoswellLifehacker
Gmail Delete Keyboard Shortcut - Works in IE, Firefox, Opera [Digital Inspiration]