If this was BuzzFeed this post would be entitled something like:
You wouldn't believe how much time you'll save from this one neat trick!
I've worked with a lot of people who know bash and its derivatives very well, but I don't think this is too widely known.
$ make me a sandwich
Oh no! We forgot we needed elevated permissions for that command.
At this point, people hit:
up left left left left left left ... sudo enter
The marginally more enlightened might go for:
up ctrl+left sudo enter
Or perhaps,
up home sudo enter
However, the quickest way is to use !!:
$ sudo !!
!! repeats the last command, but you can prepend it with sudo to gain those elevated permissions. A small thing, but one that can save quite a bit of accrued time.