Having used Fluxbox, Windowmaker, KDE, Gnome and Cinnamon, I find XFCE's start menu design the most productive. Recently used items appear on the top and you can start typing and the menu items start filtering - this happens for some other DEs as well but XFCE's matching is truely outstanding. I'm able to get to any item in less than 2 seconds (obviously I've assigned keyboard shortcuts to frequently used items) - very satisfying.