4. Towel
The Towel! Perhaps the most common/important item that throwers forget to bring to their meets. This is extra important as it can serve many features. In the wet, the towel serves as a valuable tool to not only dry your throwing implement but also the circle and soles of your throwing shoes.
Likewise, when it is hot, it can keep you cool but placing it over your shoulders. In addition to removing dirt and loose rubble that may be left in the circle. This will also come in handy during warmups and competition to practice your technique.