xterm, so I have the same on MacOSX and on Linux, and because it's very stable. Also it's very easy to create an xterm from script.
But in truth, most of my shelling (which is probably what you wanted to ask) is done with emacs M-x shell, so without any terminal emulator. (Also notice that most of the rest of my shelling, done in xterm, is actually done in screen).
