Gnuplot and Aquaterm

I mainly use Gnuplot with a "graphic terminal" called AquaTerm:

AquaTerm is a viewer app that displays vector graphics. Other apps connect to AquaTerm using a simple remote object messaging protocol. By adding 'adapters' to legacy code very little coding is needed to bring it to OS X.”

You used to have to make small changes in the Gnuplot source to use AquaTerm, but now, with Gnuplot v. 4, AquaTerm support is built in. In fact, the official binary of gnuplot for PPC Macintosh requres that Aquaterm be installed.

Note that using Gnuplot with an X Window System gives you some rudimentary mouse support (you can rotate 3d graphs, etc.), but Aquaterm is a much smaller download than the entire X installation, and is a "normal" Aqua program.