scott@9i > select * from cat;

TABLE_NAME                     TABLE_TYPE
------------------------------ -----------
DEPT                           TABLE
EMP                            TABLE

scott@9i > select * from cat where table_name !='EMP';

TABLE_NAME                     TABLE_TYPE
------------------------------ -----------
DEPT                           TABLE

scott@9i > create user test identified by test!;
create user test identified by test!
                                   *
ERROR at line 1:
ORA-00922: missing or invalid option


scott@9i >  create user test identified by "test!";

User created.

scott@9i > create user test2 identified by test@;
create user test2 identified by test@
                                    *
ERROR at line 1:
ORA-00922: missing or invalid option


scott@9i >  create user test2 identified by "test@";

User created.

scott@9i >  grant connect to test;

Grant succeeded.

scott@9i >  !sqlplus -s test/test@
SP2-0306: Invalid option.
Usage: CONN[ECT] [logon] [AS {SYSDBA|SYSOPER}]
where <logon>  ::= <username>[/<password>][@<connect_string>] | /

ERROR:
ORA-01017: invalid username/password; logon denied


^C

scott@9i > !sqlplus -s test/"test@"
SP2-0306: Invalid option.
Usage: CONN[ECT] [logon] [AS {SYSDBA|SYSOPER}]
where <logon>  ::= <username>[/<password>][@<connect_string>] | /

ERROR:
ORA-01017: invalid username/password; logon denied


^C^D