I'm quite sure that it is not possible to add PostScript, because there is no way to find a common starting for C, C++, Perl, plain TeX and PostScript.

I took that as a challenge :D

%:/*:if 0;false +s&&(#*/include<stdio.h>/*
{ Just another \TeX\ hacker,
{ \bye
} &g;print substr q q
Just another Perl hacker,
q, 1 and exit; q q
%};};);echo -ne "\e[A\e[K\
Just another bash hacker,
" && exit; */
int main() { printf("\
Just another C%s hacker,\n\
", "++"+2*(1%sizeof'2')); } /* }
/Times-Roman findfont 20 scalefont setfont newpath 72 72 moveto
(Just another PostScript hacker,)
show showpage % q # */
[download]

The starting %: is just brilliant. Congratulations! In the meantime I added LaTeX, zsh and original Bourne Shell (tested on SunOS 5.7) support. Here it is:

%:/*:if 0;false +s &&(#*/include<stdio.h>/*
{ \egroup\expandafter\ifx\csname documentclass\endcsname\relax
  \else \documentclass{article}\begin{document} Just another
  \LaTeX\ hacker, \csname fi\endcsname \end{document}
  \fi Just another \TeX\ hacker,
{ \egroup\end                   
} &g;print substr q q
Just another Perl hacker,
q, 1 and exit; q q
" (";})
awk 'BEGIN{printf"%c[A%c[K",27,27
}';sh=sh;test $BASH_VERSION&&sh=bash
test $ZSH_VERSION&&sh=zsh
echo Just another $sh hacker, && exit; */
int main() { return 0*printf("\
Just another C%s hacker,\n\
", "++"+2*(1%sizeof'2')); } /* }
/Times-Roman findfont 20 scalefont setfont newpath 72 72 moveto
(Just another PostScript hacker,)
show showpage % q # */
[download]