Along with the first answer, I'd second that particular skills, such as ambition, being proactive, thorough, asking questions, etc., are all part of an outstanding students' toolkit. Attending professor office hours illustrates interest and dedication to the topic (as most students do not take advantage of this offering).
Outside the classroom, an outstanding student is able to handle ambiguous projects that require some initiative on their part. Specifically, those that can parse out non-relevant information when working on a project (with lots of information thrown around) will be successful.
There are many more characteristics, but these are very relevant in today's workplace.