Sabayon comes in different flavours to choose.
To distinguish between them, a suffix is appended to file name.
Here's a short description. More details can be found in this thread on Sabayon forum.

main releases:

G

This version contains the well known GNOME 3.

K

This version comes with KDE SC, another popular desktop environment.

Xfce

Contains Xfce - lightweight yet very functional and friendly desktop.

experimental or secondary releases:

LXDE

With LXDE. Small, pretty and usable. In this category it's the best solution for newbies.

E17

With Enlightenment DR17.

additionally, these Core releases are available:

SpinBase

It's a very minimal environment that can be used for many different purposes: didactical, home server deployment, and even for custom Sabayon ISO images creation, using our tool called Molecule. Any Sabayon release we make is based on SpinBase.

CoreCDX

It's geared towards very minimal graphical environment setup, no fancy tools, browsers, whatever, just Fluxbox and command line.

ServerBase

It's very similar to SpinBase, but powered by a server-optimized Linux kernel (package: sys-kernel/linux-server).

OpenVZ

It's our official OpenVZ template.

All of them have a smaller footprint making them fit into a single CD, or USB memory sticks.
SpinBase and ServerBase are provided with a very minimal Anaconda Installer and CoreCDX should be preferred for non-standard filesystem/partition layouts.