Regular click response, which most of us perceive as instant.
A real life example of this is the Nielsen NetRatings tracking code, which intercepts all click events and binds a pause function that sleeps for 500ms.
When a delay is required a compromise of 100ms may be the best solution. Although you will probably perceive the delay if you compare it with the non-delayed click event above, in the real world a 100ms delay is felt as an instant response. (See Mr. Jakob Nielsen)