I'm searching for a tool like The Grinder.

What I'm searching in particular is the Functional Testing part of this tool.

I explain what I have to do:

I must test the a web application's GUI. For do that I'll use the Functional part of The Grinder.

For a better test I'm searching for a tool which has the same (or approximately) potentiality of The Grinder.

If someone could suggest me some tools I'm glad...

Thank you.