Gwave is a waveform viewer for the output of analog electronic circuit
simulators such as spice. It displays the data as 2-D plots, and
allows for interactive scrolling, zooming, and measuring of the
waveforms.
hlparse is, as the name would suggest, a Half-Life log parser and interpreter. Half-Life dedicated servers produce data output in a standard format (although they didn't in the past) which is relatively nice to parse.