Tiny utility app which places a coffee cup icon in the status bar and, when turned on, prevents your Mac from entering sleep mode.
You can choose between 'Coffee', which prevents the Mac from sleeping but allows the monitor to dim and, eventually, sleep (as per Energy Saver settings), and 'Black Coffee', which keeps both computer AND monitor always on. All you have to do is click the coffee cup and toggle on or off the desired option.
You can also create customized, timed settings. For each custom setting, you can specify the coffee 'strength' (normal vs black), the duration and an action to be executed when the time elapses (you can simply revert to normal Energy Saver settings, or you can force your Mac to sleep).