Frances O'Conner.
She doesn't get a lot of attention, but she has been cast with roles in AI (she was the mother of the child), Bedazzled (Alison/Nicole), and Mansfield Park (Fanny Price). All the parts she has played in these movies are extremely different roles and all done to perfection. One her her goals is to be able to fill any role that someone calls on her to do. Basically she wants to be the greatest actress she can be.
And she has a great mouth.