How many times have you run a command but forgot to add sudo at the beginning? How many times did you open vim instead of gvim? All that has an easy fix, instead of pressing up-left-left-left-left-left... (almost like a Konami code, isn't it?) just use !!.
!! expands to the previous command, so for example:
vim foo
, then
g!!
will execute "gvim foo".
Another common problem, you mistype vim for vmi (hey, it may be a common problem if you're dyslexic). Just type fc, short for fix command, to open the last command in your configured editor. Fix it (lxp, bonus points if anyone understand this :D) then write and save. The fixed command will be executed.