How to always show the menu bar on fullscreen mode?
I don't think it can be done.

By default, the menu bar will float in if you hover the mouse at the top.

Alternatively, why not just use the window maximised, which will give a very similar look to what you want. [Green dot, top left of any window - though some apps will toggle full screen horizontally &amp; vertically, others only vertically, you'd have to drag the corner for those]

Update for Yosemite, the green button behaviour is now reversed from Mavericks &amp; before…  


Green dot will set to fullscreen, without the menu bar.  
 Alt ⌥  /Green dot will maximise, leaving the menu bar visible.