i frequently use a local command to duplicate the marked string and
comment out the first instance (or the second depending on the cursor point).
Pretty useful stuff.

On Sun, Jan 17, 2010 at 6:19 AM, Deniz Dogan <deniz.a.m.dogan@gmail.com> wrote:
2010/1/17 alin.s <alinsoar@voila.fr>:
>
> For me it would be very convenient to have a key-binding to duplicate the
> current line.
>
> In order to duplicate it I have to press
>
> C-a C-SPACE C-e C-f M-w C-g C-y
>
> It's too much for an usual function. C-x C-a would be good?
>
> More than that, if I press C-u C-x C-a, I wish to duplicate the current
> line, and to comment the old line.
>
> Do you consider that such a function would be useful for many of you?
> Otherwise, I have to wtite it myseld in my own .emacs...
>

I have such a function bound to M-k but I never find the use for it.

--
Deniz Dogan