Vanilla OS
Vanilla OS, a fixed-release distribution based on Debian (formerly Ubuntu, prior to version 2) with the GNOME desktop, is an immutable operating system. The core parts of the system are locked down to prevent unwanted changes and corruption from third-party applications or a faulty update.
VS
Tiny Core Linux
Tiny Core Linux is a 16 MB graphical Linux desktop. It is based on a recent Linux kernel, BusyBox, Tiny X, Fltk, and Flwm.