A lot of times, when I want to save a file in vim and immediately exit thereafter, I accidentally type :Wq instead of :wq.
Vim naturally gives me this error:
You can also use ZZ which is the same as :wq<CR>
Though abbreviations suggest themselves for this (:cnoreabbrev Wk wk), their main disadvantage is that they are also applied in other places, such as when using Wk in a search pattern.
With the cmdalias plugin, you can define an alias:
:Alias Wk wk
PS: There is no :wk command, did you mean :wn[ext]? For a simple :w, have a look at this question
You can create a simple vim command that is basically an alias for wq. Place the following in your ~/.vimrc file:
command! Wq wq
For more help see:
:h :command