If you want the position or a second interview say something like this:-
"Mr. Employer, I am very impressed with what I have seen here
today - your company, its products and the people I have met.
For a Sales Type position
"I am confident that I can do an excellent job in the position
you have described to me. [ How soon will I be able to start?
] or [ When can I arrange a second interview? ]".
For Positions requiring less assertiveness / sales techniques
"I have enjoyed talking with you. The job sounds excellent. [What are
your thoughts about me? ] or [ Do I have the right sort of experience
that you are looking for?]"
This gives you a chance to hear the interviewer's impressions and to
respond to any negative thoughts or misunderstandings that may have
arisen.
The employer will be impressed with your enthusiasm. If they
make an offer then accept it.