Any discussion of "first line of defense" should be about fences, motion sensor lights, landscaping, good doors and locks, and alarms.
Jumping into weapons is missing the point of the first thing you should be doing to keep your home safe, which is motivating bad people to go elsewhere and keeping them from getting in or slowing them wayyyyy down in their efforts.
Define your boundaries. That doesn't require a 10ft wall with spikes. Simply establishing a border that someone has to make an effort to cross establishes a psychological barrier. You can do this with hedges or classic "picket" type fences. As uncomfortable as it might make us, motivating people to go to the neighbor down the street that just has a manicured lawn without a clear boundary helps us avoid dealing with intruders.
Remove concealment. If you want bushes and landscaping try to keep the types that people can hid behind well away from the house and force them to cross open ground where they risk being spotted. If you just have to have something "pretty" up against the house, make sure it has thorns that can't be avoided if you're putting it under windows or near entrances. Try to pick plants that are too short to hide an intruder or that are going to hurt to get between a wall and the plant.
Lights. Flood lights make it uncomfortable for people that don't want to be seen to get to the house at night. Add in motion sensor lights (remarkably cheap LED solar powered motion sensor lights are now available that just tack up to trees, posts, fences, and walls) as floods or spots to light someone moving around and put them "on notice" that they're not moving freely. A mix of hard wired floods on the house and buildings, hard wired motion sensor floods, with solar powered LEDs scattered around where people would approach the house makes it as close to impossible to approach without setting off a light or being seen.
Doors and windows. Most exterior doors are not a good barrier and windows are usually even worse. Doors should be hung with deck screws long enough to sink into the structural framing around the door. It is an easy retrofit for a home owner or renter to pull the old screws from hinges (one at a time) and strikers and replace them with 4 inch and longer deck screws. Replace your deadbolt with a long throw deadbolt so there's enough material in the striker to make those long screws work for you. Exterior doors with windows or "lights" need to be reinforced instead of easily broken glass. That can be retrofitted if you don't mind the decorative ironwork security bolt ons. If you can replace a door with steel or fiberglass and you mount it solidly into the framing it can make it very difficult for a would=be intruder to get in. Put a keyed on both sides deadbolt in place if you have any sort of window in the door so a reach in through a broken window won't allow the door to be easily opened. Add in a wired or wireless camera so you can see who is at the door before opening it (while they blink at the motion sensor light flooding them with photons) helps you know who's there. They're available with bluetooth so you can sync them with your phone to look at the vid from anywhere in the house and even communicate with your wifi to see the vid even when not at home. Windows become a more difficult problem since you want to be able to see out and let light in, but there are security films that resist breakage and there are locks even for your windows. Simply putting a nail through the frame of a double hung window can keep it from being slid open if you don't want to spend money on locks. Keep your ladders put up and out of sight so they aren't used to get to windows or balconies.
Alarms. There are endless options now in addition to the monitored alarm companies. Simple little screamers that you attach to doors and windows to wireless and wired systems sending information to your computer and phone. These allow you to put any number of exterior, perimeter, and interior sensors in place that tell you if someone is present and/or "tell" them they're detected. They can also "tell " the would-be intruder that they've been reported to the owner and authorities. People often forget that they can put sensors outside their house to tell them if someone has crossed the property boundary you established. Driveway sensors have been around for years that tell property owners that someone has pulled off the road and onto the driveway. Why not add sensors outside to tell you if someone is approaching before they get to the door/window? The same goes for interior spaces as well. Think about being able to monitor not just the doors and windows, but movement within the house using sensors communicating with phone/tablet/computer. It can also help you keep track of the kids.
Dogs. I have had pets as far back as I can remember. Some of them were protective of the house and wouldn't let anyone put a hand on the door and others would only demand affection, but we've always had one that makes noise if a stranger approached the house. "Attack" dogs can be a liability, but noise makers are organic alarm systems that have to added benefit of creating doubt in the mind of a would-be intruder about their safety (if the critter has a deep enough voice). My wife's family had a wiener dog that sounded like he was 100lbs of furry death that made strangers very nervous approaching their house, but even small "yappy" dogs are good alarms. If you want "guard" dogs you need to have the training, yes, You, not just the dog, to safely handle them. Another "dog" approach is to get a large dog house and place it so it is just visible from the street. Even if your pet weighs pounds instead of tons, the large dog house tells the bad guy driving by looking for easy targets that there just might be something monstrous at your house they don't want to deal with.
Interior. If everything has failed to keep an intruder out of the house understand that you can do things that make it difficult to get to you and your family. That also requires forethought and planning about where the most precious thing to you (family) can be separated from the threat of an intruder. Try to keep the kids rooms well away from the exterior doors and out of easy reach of windows from ground level. Try to put your bedroom between those exterior accesses and the kids. Put independent motion sensor lights between the exterior accesses and the kids and you so the intruder is triggering lights and you aren't. Understand that once inside an intruder is a real threat, but your best option is to "fort up" and hold the safest part of the house with your family in it against the intruder instead of searching in the dark for a bad guy. Make a plan and practice it with family members just like you should be making a plan and practicing it in the event of a fire. Monitor movement inside the house from your tablet/computer while you talk to 911 about the intruder. Never get off the phone with 911. They're your communication conduit to the responding authorities and you want the people responding to know you and your family are holed up in the house and that you aren't prowling the property. Put a house key on a light stick or some sort of flashing red light (plenty of cheap bike flashers) that you can toss out a window for the police to enter from their approach instead of hunting for the open door/window. As strange as this may sound, put on something distinctive that is easily recognized by the responders and give a good description to the 911 voice on the line. You don't want to be a victim of misidentification by armed responders. Something bright and easily seen at night when the flashlights are on you. Also, don't go rushing out to the responders like you're some "homesteader" shouting at Marshal Dillon to "They went thataway!". You're primary goal is keeping your and your family safe and that means making sure the LEOs know you're the home owner and not some shape in the night rushing at them they feel threatened by because YOU called them there over a threat. It goes without saying that you don't want a weapon in your hand when your encounter them, but think about a what the phone in your hand looks like to them as you wave your arms about so try using a headset and keep the phone in your pocket (it also keeps your hands free in the house while you're handling a weapon and talking to 911 while keeping your family holed up ).
Your first line of defense is keeping people off your property and out of your home.
