Cannot have ! in oracle password?

I am not able to put the exclamation point in a password:

demo40@ORCLDEV> create user testtest identified by testtest;

User created.

demo40@ORCLDEV> alter user testtest identified by test!test;
alter user testtest identified by test!test
*
ERROR at line 1:
ORA-00922: missing or invalid option


demo40@ORCLDEV> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE 10.2.0.1.0 Production
TNS for 32-bit Windows: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production

demo40@ORCLDEV>




Any idea why?

Code:

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SQL> grant connect to test1_user identified by test!pass;
grant connect to test1_user identified by test!pass
                                              *
ERROR at line 1:
ORA-00933: SQL command not properly ended


SQL> grant connect to test1_user identified by "test!pass";

Grant succeeded.

SQL> conn test1_user/test!pass
Connected.
SQL>

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Nonquoted identifiers can contain only alphanumeric characters from your database character set and the underscore (_), dollar sign ($), and pound sign (#). Refer to Schema Object Naming Rules.