Gwave is an analog waveform viewer which is used to view the output files produced by ngspice or gnucap. Here are some feature suggestions. You might choose a large handful of features to implement as your GSoC project.
This project involves improving the integration of gwave into the interprocess-communication to and from the other tools, especialy gschem and gnucap. While gwave has an X11-based remote mechanism, Dbus is now the standard, and should probably be used instead.
Gwave has been ported to Gtk2. As part of this effort, developing a battery of unit tests for gwave would be useful. The idea is to create a variety of different input files which exercise gwave's ability to import and display waveforms. An important feature for testing will be to compare the displayed waveform against a “golden” waveform to verify rendering correctness.