DB2 passwords with special characters
This is a long-standing bug in the GUI tools.

However, as long as your password does not contain a double quote (") character, then you can work around this by putting double quotes around the password to connect.

connect to sample user test using test!
--&gt; SQL0104N

connect to sample user test using "test!"
--&gt; connection succeeded.


This method will also work if the GUI tools prompt you for a password with a dialog box.  

If you have passwords with double quotes in them, you may be out of luck.  You could open a ticket with IBM DB2 support and/or just change the password.