How to disable fancy visual effects in Gnome Shell?

The extension 'Disable Window Animation' don't work any more in Gnome 3.8, so just do this command to disable it:

gsettings set org.gnome.desktop.interface enable-animations false

It's possible to disable window animations with this extensin from extensions.gnome.org. You may have a look here:

https://extensions.gnome.org/extension/119/disable-window-animations/

In Gnome Shell you can't disable any effect. Why? Because AFAIK there's not a tool à la CCSM that Handles this for Mutter.

In Unity 3D you can disable most effects with CCSM.

LXDE is fast, and lightweight it uses Panels and is GTK+ compatible so Themes for GTK 3 & 2 will work.

I ran an LXDE+Compiz setup that was fast, responsive, and light even if I didn't need it to be light.

A very light alternative to Compiz is xcompmgr it provides basic compositing, compositing is needed for most Docks (AWN and Docky need Compositing for Transparency).

I wouldn't say XFCE is not light anymore but it's definitely heavier than LXDE.

So if you're looking to save RAM this is not really an Option.

Enlightenment looks just awful and it uses the same amount of RAM and CPU as LXDE.