Guake terminal
Guake is a top-down terminal for Gnome (in the style of Yakuake for KDE, Tilda or the terminal used in Quake). Guake is already package by a number of distribution (among them are Fedora, Debian, Ubuntu or ArchLinux).
A Windows-oriented version of the popular Guake Terminal for Linux.
winguake A Windowsoriented version of the popular Guake Terminal for Linux.
portable command-line terminal-client