One may need different things depending on the location and also the number of people traveling. If it's a large group, one can share some items so as to reduce the weight of luggage. However, some essentials like a first aid kit should be strictly carried so that they come to the rescue in an emergency. Here is a list, which will be helpful to you.
It would be silly to go for a beach vacation without carrying along a bathing suit. So, carry it with you.