   su2 is a great program for anyone that has anything to do with
system administration.  su2 gives you the ability to masquerade with
the UID of other users.  You use own password to switch.  Probably the
biggest benefit of su2 is that you retain your own customized shell
environment.

   For the most part, this program is used by system administrators to
become root, but su2 has been written to enable much more flexibility
than this.  Regular users can put a .su2rc file in their home
directory to enable other users to become them.  While this may sound
odd, it is sometimes useful to allow a number of users to masquerade
around with the uid of restricted accounts.  One such example of this
is a 'www' account which is a common occurance with the proliferation
of the web.  While the www user's password may be starred out to
disable direct logins, root could put a set of user names into
~www/.su2rc to enable these users to 'become' www and do Web
administration.  [This feature can be disabled if you are worried
about 'account sharing.']
