Unnecessary Users and Schemas?

In my Designer 9i repository I've identified a number of Users and Schemas that I'm wondering if I could remove without damage. I've already removed the HR and SCOTT schemas since I know those aren't necessary but I have questions on a number of other users.

Can anybody tell me which of the following users and their schemas are safe to remove?:

USER                                    DEFAULT TABLESPACE
---------------                        ----------------------------
ANONYMOUS                    XDB
CTXSYS                               DRSYS
DBSNMP                              SYSTEM
MDSYS                                 SYSTEM
ODM                                     ODM
ODM_MTR                           ODM
OE                                         EXAMPLE
OLAPSYS                             CWMLITE
ORDPLUGINS                      SYSTEM
ORDSYS                               SYSTEM
OUTLINE                              SYSTEM
PM                                         EXAMPLE
QS                                         EXAMPLE
QS_ADM                              EXAMPLE
QS_CB                                  EXAMPLE
QS_CBADM                         EXAMPLE
QS_CS                                  EXAMPLE
QS_ES                                   EXAMPLE
QS_OS                                  EXAMPLE
QS_WS                                 EXAMPLE
SH                                         EXAMPLE
WKPROXY                          DRSYS
WKSYS                                DRSYS
WMSYS                                SYSTEM
XDB                                      XDB