Race Belt: For most races, you have to wear your race bib during both the bike and run portion. Often you wear the bib on the back for the bike and the front for the run. A race belt allows you to quickly and easily spin the bib from front to back without losing precious seconds in transition.
Bungee or elastic laces: No need to fumble while trying to tie shoe laces in transition. Make sure you put the bungees in early enough that you can get another pair if you break them... I learned that one from experience at the Early Bird Tri, when I tried putting my laces from last season in my shoes, only to realize they had totally fallen apart. You can cut your bungees to size too, just use a lighter and burn off the cut ends to make sure the elastic doesn't unravel.
Water bottles with squirt tops: You want to be able to easily drink while on the bike. If you don't have a hydration system or an aero bar water bottle, you may want to look for water bottles with squirt tops. I really like the CamelBak Podium Chill. It fits in my bottle cage and keeps the water cold!
Body Glide: Put wherever you think you may experience chafing. I like to rub some onto the heel of my running shoes, as well as the spot inside my running shoes that sometimes gives me blisters.
Baby Powder: Pour some into your bike shoes and your running shoes to help dry your feet.
Plastic grocery bag and gardening gloves: I have used the plastic bag trick to help put on my wetsuit, and recently learned that wearing gardening gloves helps prevent you from tearing your wetsuit as you pull it up! Place your foot in the plastic bag, then slide your foot into the leg of the wetsuit, once you have your wetsuit adjusted to the right height on your ankle, remove the bag.
And to make sure that you have everything you need, here is my ultimate Race Day Checklist!
Tell me, is there something that you can't live without on race day?