DeuTex is a tool to work with WAD files for Doom, Heretic, Hexen, and Strife.
It can be used to extract the lumps from a WAD and save them as individual
files.  Conversely, it can also build a WAD from separate files.  When
extracting a lump to a file, it does not just copy the raw data, it converts
it to an appropriate format (such as PPM for graphics, Sun audio for samples,
etc.).  Conversely, when it reads files for inclusion in PWADs, it does the
necessary conversions (for example, from PPM to Doom picture format).  In
addition, DeuTex has functions such as merging WADs, etc.  If you're doing
any WAD hacking beyond level editing, DeuTex is a must.