Absolutely have a mini sewing kit with scissors. I just got married on friday and it was needed by a few people! I also used some mints, spray deodorant and vaseline for blisters from my shoes! Aspirin is always a good idea, as well as water and a snack since it's a long day!
White chalk, anti diarrhea meds, sewing kit. A dry wash cloth. I used this to rub black scuffs off of my best friend's train before she walked down the aisle. The friction will lighten it, and unlike a stain remover kit, or chalk, you don't have to worry about it messing up the fabric.