When identifying the odd one out, consider the category or common features shared by most of the items. Look for the one that doesn't belong based on characteristics like physical activity, objects used, or categories.
In this case, the odd one out is Chess because:
- Cricket, Hockey, and Football are all physically played sports that involve a ball.
- Chess, on the other hand, is a board game and does not involve a ball.
Thus, Chess is the odd one out.
Therefore, the correct answer is \( \boxed{2} \).