I can kill you with my brain
And then there's the students who have done all the clubs, volunteering, AP classes, etc but have gotten no joy or learning out of any of them, because they've been told that they "have" to do those things to get into a good college.
It's not about doing all the clubs, etc. It's about doing something meaningful to you, which you can talk about. Especially for the elite level US unis, it's about focus, not breadth. Showing real devotion and interest in something - be it an activity, a cause, an academic interest, what have you. But doing tons of clubs and etc. just for the sake of doing tons of clubs isn't going to get students into anywhere.
Likewise, the idea of a "well rounded student" - not necessarily going to help in terms of college admissions. Total myth that you need to be well rounded, as students tend to interpret those words.