Recently I added the following lines to my ~/.emacs file:

;; Don't insert tabs when indenting regions
(setq-default indent-tabs-mode nil)

The idea behind disabling the indent-tabs-mode was that (especially) while programming I want any tabs to be converted to spaces. Since different people have different settings for a tab width this seemed like a good choice.
However, once I opened a Makefile I ran into trouble. In a Makefile tabs are a requirement, not an option. Since all my tabs were converted to spaces the moment I saved a Makefile compiling became a nightmare. To solve this problem I added the following to my ~/.emacs file, after the aforementioned statement:

(add-hook 'makefile-mode-hook
          (lambda ()
            indent-tabs-mode t))

This enables tabs again for modes that involve Makefiles.