Planning nondegree classes I am thinking of registering for nondegree classes at a local university to give an impression to future admission comitee that my GPA does not really reflect me. But I have some concerns. How should I choose which courses to take.

If some internationally known professor gives an introductory course e.g. Introduction to Algorithms and if another internationally unknown one offers advanced graduate course, which one should I choose first ? Consider the future recommendation letters to United States schools I would expect from them.
The reputation of the faculty member helps somewhat, but is nowhere near as useful as the quality of the recommendation letter. A letter from a famous person who doesn't really know you outside of the classroom (or doesn't know you at all) isn't nearly as helpful as an in-depth evaluation from someone you know well, and who knows you well.

However, I find the notion that you would taking an introductory course versus an advanced elective somewhat concerning. In general, if you are looking to buttress a graduate-school application, evidence that you can handle graduate-level work in the field matters far more than having a Big Name write you a weak letter.