My cat once deterred a home intruder back when I lived in a very shitty first floor apartment across the street from several very cheap bars. I had a rack of DVD's by the front door next to a small table like area where I'd put my keys. My cat would be sitting there when I got home, or when outside sounds got interesting, and occasionally he would knock over that DVD rack when he'd leap away, especially if a loud sound scared him.

then one time I got home to a busted lock and a slightly open door. I tried to run in, but that dvd rack had fallen forward from him kicking off of it, bounced off the wall, and landed between the door and the wall, essentially wedging it closed. I had to hulk it open, crushing the dvd rack, but that had kept the intruder from actually getting in. My cat was panting in panic, so it probably happened only minutes before I got there. I made sure that cat lived like a king for 15 more years.