If you bring con food, for the love of god make sure to pack utensils. My con friends gathered 'round for a supper of cup ramen (three cheers for coffee machines) and found ourselves in a bind when we didn't have anything to eat with. We ended up using ice tongs and coffee stirrers. Don't be like us.
Also, make sure to bring a small sewing pack and fast-setting glue. You never know when an emergency will strike.