XMonad + Gnome 3 $HOME/.xinitrc /usr/share/applications/xmonad.desktop /usr/share/gnome-session/sessions/xmonad-gnome.session /usr/share/xsessions/gnome-xmonad.desktop

.xinitrc

#!/usr/bin/fish

exec gnome-session --session=xmonad-gnome "$argv"

gnome-xmonad.desktop

[Desktop Entry]
Encoding=UTF-8
Name=GNOME XMonad
Comment=This session starts XMonad with GNOME
TryExec=/usr/bin/gnome-session
Exec=gnome-session --session=xmonad-gnome
Type=XSession

xmonad-gnome.session

[GNOME Session]
Name=GNOME Xmonad
RequiredComponents=gnome-settings-daemon;
RequiredProviders=windowmanager;notifications;
DefaultProvider-windowmanager=xmonad
DefaultProvider-notifications=notification-daemon

xmonad.desktop

[Desktop Entry]
Type=Application
Encoding=UTF-8
Name=XMonad
Exec=xmonad
NoDisplay=true
X-GNOME-WMName=XMonad
X-GNOME-Autostart-Phase=WindowManager
X-GNOME-Provides=windowmanager
X-GNOME-Autostart-Notify=false