1.)Race medal - Everyone gets one just for finishing the race. Finishing makes you a winner. (Overall and age group winners often win money, shoes, or another prize.)
2.) Pretzel thins - Yum, carbohydrates.
3.) Corn snack - Some other promotional carb snack that may be worth trying. Or it might taste like cardboard.
4.) Peanut butter - Yum, protein.
5.) Body lube - Don't laugh. You will need it, especially if it's hot. Otherwise your body parts will rub together and you will chaff or even bleed. Don't let this happen to you.
6.) Race number - A nice memento.
7.) Shaving oil - They promote non-chaffing, also no nicks or cuts.
8.) Anti-fungal cream - Itchy foot happens.
9.) Lotion - My boyfriend calls Utterly smooth, "Boob creme." It it works for cows utters, it must work for humans too.
10.) Vaska laundry detergent - Promoting green laundry. Not green like the color. Green, laundry.
Oh, and of course the race t-shirt. They usually give a free cotton shirt. Sometimes, for a price, you can upgrade to a technical t-shirt that will keep you cooler and wick sweat away from your body. For an extra $6 it's much more comfortable than exercising in cotton.
Thanks for LK for the post idea!