The command line way of getting 1 file out of a rpm is to rpm2cpio.
rpm2cpio <rpmfilename> > <filename.cpio>
Now you have a cpio archive which you can use to get files out of.
Or:
rpm2cpio <rpmfilename> | cpio -idv
And one more:
To extract a single file from a package
rpm2cpio gnupg-1.2.6-6.src.rpm | cpio -ivd gnupg.spec