"Insomnia" was great -- I think that was Christopher Nolan's film immediately after "Memento." Robin Williams had two outstanding performances as villains that year, "One Hour Photo" was the other.

If you ever get a chance, Nolan's film was a remake of a Norwegian film (same title) starring Stellan Skarsgard. The original is excellent as well, much more focused on Skarsgard dealing with his psychological downslide.