The built in terminal window on Mac OS. Totally not bloated, does what it should in a 'lean but mean' way.
Terminal (also referred to as Terminal.app) is a terminal emulator included in Apple's Mac OS X operating system. It originated in Mac OS X's predecessors, NEXTSTEP and OPENSTEP, and allows the user to interact with the computer through a command line interface. On Mac OS X, Terminal is located in the /Applications/Utilities folder.
Productivity Developer Tools Utilities
shell terminal-client xterm