The hazards of a hurricane can vary depending on whether you are inland, near the shore, on a boat on the ocean or on a boat on a lake or river. Although some of the hazards are common to all or more than one venue, their threat level may depend on where you are.
If you are inland: The biggest threats are the same as those associated with severe thunderstorms. High winds can down trees, damage roofs and cause outside objects such as lawn chairs and flower baskets to become airborne and break windows. Hurricanes can also spawn tornadoes which can magnify all of the following hazards. Additional problems are flash flooding for roads and basements. Lightning strikes can be deadly and down trees. But they can also send flames through the ground to your house and send a power surge to ungrounded electrical equipment that can set your house on fire.
If you are at or near the shore: All of the above hazards apply, except maybe for downed trees. The greatest hazard for people who live at the shore is the storm surge, which is a wall of water driven onto land by hurricane force winds. Search "storm surge" on wikipedia. It can destroy homes. Another hazard is erosion caused by the storm surge and heavy rains. Hurricanes always cause flooding at or near the shore. If you live in the southern half of the United States, you need to be watchful for water snakes and other dangerous critters that may have migrated into the flood zones. Hurricanes also inflict the worst water damage on beach or shoreline homes. The biggest after-storm risk is probably mold. Some types of mold can make people seriously sick. Check out http://weather.about.com/gi/view/mmwrhtml/rr5508a1/htm.
If you are at sea: Trees are not an issue, obviously. But the wind and waves are. The waves and swells (dips) can cause the ocean to be higher than the boat. I've seen it. There is also a hazard called a "queer wave," which is a wave that comes along unexpectedly that is much bigger than the other waves. Based on my own experience, be careful if you are on a cruise or other excursion and are collected by a hurricane. Unsecured objects in your cabin can hurt you when things go badly. You can be walking around and the floor will suddenly drop. You might be sitting in an unsecured chair or couch and the boat can lurch and you may be launched across the room.
If you are on a boat on a river or lake: Get out of there. The winds and waves could sink you easily. Tornadoes can form waterspouts, which are deadly.