For me, a 120lb dog seems to do the trick for the majority of people.. He scared a pizza delivery guy into dropping my food just last week! You really can't beat a dog when it comes to protecting your home/family.
As for the guns, I don't know about you guys, but I keep my shotgun under my bed. In his case, that would have hurt him (The guy was in his bedroom!). I generally keep a handgun handy (Computer/TV, go figure? lol) that I carry with me. I tend to opt for 45 ACP as do most (Glaser Blue Dots in my EDC, Coron DPX in my Sig which stays in my truck).
As for shotguns and home defense, two things that I haven't seen stated in this thread. DON'T GO STOCKLESS!! Yes it seems like it would be easy to handle, but they aren't nearly as accurate, less so when you need it.
Secondly, find an SBS if it's allowed. Where I live, if you pay the taxes and wait the allotted time, you can own a lot of things you wouldn't normally think possible.. I have a Mossberg 590A1 SBS (14") it's amazing for those hard-to-reach dirtbags :P
I also tell people to stock up on roach spray as stated above. It's way more effective than mace, even if it doesn't burn they won't be able to see. That one's even good for offices (My Ex was a teacher, I made her keep a can in her desk