I'm playing an unarmed character in Fallout 1 right now, and I think it would just be really neat if God Hand music started playing whenever I got into a fight.
I remember there being a .wav to .acm (the Fallout music format) converter. Just check NMA's download database. After you've done that just rename your new acm to one of the existing music files (it's usually per map) and you should be all set.