I think that Mr. Smith and Mr. Wesson make the best protection against a home invasion... but I do have an alarm system installed on the house (and walls) and highly recommend them.
Be careful not to be lazy with alarm coverage though. I have heard of several houses being burgled even though they had alarms.
The first one had all doors and windows alarmed, but no motion detection so the burglars lifted roof tiles and just dropped through the attic access hatch.
Another was where the homeowners were just lazy. They were in the back yard pool so saw no reason to set the alarm. Probably seeing or hearing that they were in the pool some enterprising person broke in the front of the house and quickly made off with money and jewelry.
The third home I heard of had only motion detection alarms and they intentionally set the detectors to allow them a pathway from the bedroom at night down a hall to the kitchen so that they could get up and get something to drink or a late night snack without turning off the alarm. Someone who somehow knew this (alarm installer or friends of alarm installer?) broke in when they were out and only stole what they could from that unmonitored area without going into the rest of the house and setting off the alarm.
And yet another one was a two story home and the occupants thought it would be enough to just alarm the ground floor windows and doors. The thief used a ladder to get to a roof skirt on the first floor level and then walked it to a second floor balcony where he broke into an un-alarmed room.
Alarms are great as long as you do them correctly, use them diligently, and have an installer you can trust. Nothing backs them up like dogs in the yard, security lighting on all night and last but not least, a Smith & Wesson 9mm or 357 magnum close at hand in the bedroom when you're in there. And with the S&W you don't even have to get as close to the intruder as you would with pepper spray!
Arm the rest of the house from your bedroom at night with the remote controller, as soon as they enter the house a 120dB siren goes off and they run away. Remote also has a panic button allowing you to set off alarm if you see or hear someone outside.
