I assume since you're a "scientist," you mean to plot real data. There are many numerical and plotting packages used by professionals, with MATLAB being the most popular one most likely, especially among physicists, applied mathematicians and the like. If you're up for something more daring (or don't want to shell out hundreds of dollars), I would go with an open-source solution like the Python scripting language, specifically using the matplotlib module for 2D plotting and the mayavi module for 3D plotting. I know some version of matplotlib supported 3D plots as well, but this has been abandoned in SVN and I don't know how far along the official releases are. Alternatively, if you want something more MATLAB-like, GNU Octave is an open-source package that has the sole purpose of being a carbon copy of MATLAB's command line interface. It even recognizes M-files generally. If you're in this business, you've probably already used the packages you know you want to use, and they probably have Mac versions. Just Google around for the stuff you know and love.