Here a link to a recent article from USA Basketball, a helpful basketball resource. All of us in player development would have our own list.
Here are a few items that I would include on my list:
1) Play both ends of the floor; everyone must defend...NO exceptions.
2) Finish off the dribble consistently.
3) Develop separating moves to both the right and the left.
4) Shoot consistently from differing 'setups' (off the catch, off the dribble, coming off screens, and off pump fakes.
5) Cut proficiently.
6) Identify quality shots...taking better shots informs better shooting.
7) See the floor and pass off the double team; every great player makes others better.
8) Excel at the free throw line.
An obvious bonus providing great dividends is extended shooting range. I see too many players try to extend their range without general shooting proficiency.