Theft and drunk driving are probably the biggest. People are less aware of their belongings when they are very busy. One thing to never do is take bags to your car after shopping at one store at the mall, then go back in to shop at another store. When things are really busy, you probably won't spot someone who is casually observing and looking for a car to break into. If they see you deposit things and go back in, they know they have a window of time to break in, steal the items and anything else left in the car and get away before you return.
Drunk driving is also way up during the holidays. My family has always tried to avoid driving later at night when people are more likely to be on the road drunk. If you have friends of family members drinking at a gathering, keep an eye on them and make sure to remind them that some one needs to stay sober to drive them home.