Would like to check  whether is there any preferred/recommended  testing tool that can be best suited for SFDC(Salesforce) application for Test automation or can we use any tool(eg. QTP/Rational) to do that.

The Automation test that we refer hear is aimed to decrease the Duration of execution and can include below Test Automation Frameworks.
 -Creation of small,independent scripts that represent the modules are then used to construct larger tests to realize specific business scenarios.
 -Data driven tests that read input values from CSV/Excel files that can be used in the coded scripts for creation of objects like Contacts/Accounts etc.

Regards

Gopi chand P