GTKWave is a new tool for me, so I'll use this space to post useful tips as I discover them.
The first tip comes from Tony Bybell, author of GTKWave, who pointed
me at some helpful functionality in a recent blog comment. You can
enhance GTKWave's waveform display by replacing the normal data
presentation with something of your own design. So, for instance,
instead of looking at an opcode of "8033", you can see the disassenbled
inc $fp 3. You do this by implementing a program
that reads raw values from stdin and writes translations to stdout, and
then attaching this program as a filter to one of your signals.
I wrote a quick moxie disassembler in lisp (gtkwave-opcodes.lisp), and it is proving to be very handy!