Gnuplot - 5.05MB (Open Source)
Gnuplot for Mac is a portable command-line driven graphing utility for Mac OS X, Windows, OS/2, VMS, and many other platforms.
Gnuplot for Mac is able to generate both 2D and 3D plots; delivering the results in animated views. You can also save the graphs to a variety of image formats, including PNG, SVG, JPEG and EPS.
Supported outputs include:
Gnuplot for Mac was originally created to allow scientists and students to visualize mathematical functions and data interactively, but it has grown to support many non-interactive uses such as web scripting. It is also used as a plotting engine by third-party applications such as Octave.