Depending on weather, I may carry a light jacket/gloves/etc with me. As a general rule, the faster you go, the less you will need. The slower you go, the more gear you should bring.
But no matter what, I always put the following into the bag that they give you when you pickup your bib:
Full change of clothes (pants, shirt, etc)
Small (hand sized) towel
Snickers Bar (you can also buy one at the summit house)
This way I'm covered no matter what happens at the top.