Practical things are great. Earbuds, phone chargers (cords and USB wall plugs), battery banks, carabiners, mini Sharpies, flash drives, screwdrivers/screwdriver kits, t-shirts.
Also, I just mentioned these in another thread, but
glove belt clips are super useful, especialy since every drive team is going to be using gloves. I know you can get these customized with logos and such, just not sure where.