I curse myself whenever I think about it. For the longest time, I didn't know about this shortcut. I missed it terribly, but I was too thick to understand that I can search through the manuals or internet to find if such a shortcut exists... I used it a hundred times daily (Java, Eclipse), but the need for it is much greater in CoffeeScript+Node.js
Ctrl+Shift+D duplicates the current line by default (or the current selection, if any).
Ctrl+Shift+K deletes the whole line.
Ctrl+K twice deletes to end-of-line.
Ctrl+K Ctrl+backspace deletes to beginning-of-line.
Combine duplicate, move up/down, and the Ctrl+D multi-cursor stuff, and you have a copy-and-paste coder’s dream editor. ;-)