Which course will create impact on the admission in MIT?

There isn't necessarily one specific extracurricular that will create an impact. You really want to express yourself and make sure you ECs align with your interests. From there, take that to the next level and keep expanding on that specific activity, creating a strong interest in a few particular activities that would most definitely show the admissions officers your interest. And this could be absolutely anything (for example, even if you're interested in Aerospace Engineering, the EC can be absolutely anything, as long as your show your interest, and it is not something that is padded on to your application).

But for a particular course, almost every applicant to MIT would be taking a very challenging workload. Just align your courses to your interest of major and do well in those challenging classes.