The number of times, early in my career, I had senior engineers come and hold impromptu learning sessions is one of the reasons why I'm such a good engineer today.

Being able to have robust discussions about software engineering, best practices and design patterns and all that good stuff and have other engineers hear that discussions happening and stop by to give their input is incredibly valuable to both personal growth and oftentimes the success of a product.

Spontaneous collaboration is a big one for me. I am in a niche department and by simply having an office in an accessible hallway with my door open, people suddenly remember that my department exists and they are constantly popping in my door to chat about ideas. Usually those chats result in new projects