This is not helpful. Please stop posting this garbage.
Back to the OPs question--an example of something I did to challenge myself in college was to take up american sign language. It was something genuinely interesting to me but also very difficult to master for a number of reasons (differs completely from other languages since it's visual vs auditory, learning and respecting cultural differences between the hearing and deaf community, and difficult to find ways to practice unless you immerse yourself a bit into the community). I loved this and it actually didn't come up at all in my AMCAS, but was mentioned briefly in a few secondaries and a few times in interviews as it seemed to fit. These kinds of genuine endeavors aren't necessarily one of those things you'll use to "check all the boxes" for your application, but will come up later on in the process that will help show much more depth to your character and perspective.
Essentially, do something out of your comfort zone. Do something that will help you grow and will give you depth. It can be almost anything, but might have more significance if its not directly premed/healthcare related.
