Gnome classic

_$: apt-get install gnome-session-flashback
_$: apt-get install gconf-editor    # Ubuntu <= 14.04
_$: apt-get install dconf-editor    # Ubuntu >  14.04

24-hour clock

_$: dconf-editor

com/canonical/indicator/datetime -> time-format: 24-hour

_$: dconf-editor

org/gnome/desktop/interface -> menus-have-icons: True

Move minimize, maximize and close buttons to the right side where they belong and get off my lawn.

_$: gconf-editor

apps/metacity/general -> button_layout: :minimize,maximize,close

Alternatively (Ubuntu >= 14.04):

# Original settings
_$: gsettings get org.gnome.desktop.wm.preferences button-layout
'close,minimize,maximize:'

# Change them
_$: gsettings set org.gnome.desktop.wm.preferences button-layout ':minimize,maximize,close'
_$: gsettings get org.gnome.desktop.wm.preferences button-layout
':minimize,maximize,close'