This was my answer to a similar question a while back.
Stopped 2 burglars who had broken into my house to steal my TV and held them at gun point until the authorities showed up.
This was during law school when I was living in a house with 4 other guys. The house we lived in was prime location for the school. It was on a side street about 3 blocks, a 7-8 minute walk, from campus. While it was on a side street, it still got a lot of traffic from students walking by or riding bikes by and it was across from a university apartment complex. The university is a pretty stereotypical "State U"; a party atmosphere, about 20k students, etc.
Anyway, me and my 4 roommates all had our own vehicles that we parked out front and there was space for one vehicle in the back. The night of this incident 3 of my roommates were out of town and I think the other was at his GFs place, while my vehicle was parked in the back. So passersby and onlookers, who had seen how there were always cars parked on the street in front of the house and there weren't now, probably thought the house was empty/everyone was gone/etc. This is how I think the house got targeted and the police thought the same. Anyway, so it's just me in my house and I'm in my bedroom on the main floor. It's around 2am. I was trying to go to sleep, but couldn't, so I sat up and was reading. I heard a kinda loud "pop" that seemed to be coming from the direction of the front door. I initially didn't think anything of it, but then I hear more noises and the door open. I got out of my bed and put my head to my door to listen to see if anything was happening. I heard people walking and something like "get the TV" or "the TV is there, get it". There were no lights on in the house, neither in the living room where they were or in my room. So at this point I grabbed my Sig, grabbed a mag, and quietly opened my door. I was barefoot so I wasn't making noise that way. I open my door, stepped out slightly and peaked my head around the wall. In the darkness, I saw the outlines/shapes of 2 guys trying to unhook the TV from the DVR/speakers.
I then stepped out from behind the wall, turned on the lights, and with my gun aimed at them and ready I yelled something like "FREEZE STOP MOTHER FUCKER, PUT YOUR FUCKING HANDS IN THE AIR OR I WILL SHOOT YOU DEAD". They were obviously startled. They turned around and I think before they could process what happened they looked kinda aggressive. However, they turned and saw me aiming right at them from about 7 feet away. Once the processed this, that I was armed and may shoot (I would), they backed down. I kept yelling at them; partly to intimidate and invoke submission (this is why cops do this) and partly because I was fucking furious. One guy had a crowbar that he apparently used to jimmy the door and the other guy had a 6" hunting knife in his belt. I told them to drop the crowbar and sit on the ground legs crossed with their hands up. I kept repeating that if they tried to run or do anything I would kill them. I was yelling at them that if they moved an inch I would start shooting. I just remember being "red" at this point. The gravity of the situation hit me and I was angry as hell that these shitheads broke into my house and tried to rob me.
I gave a roll of duct tape to one of them and told him to tape his partners hands together behind his back. I had my gun trained on them and let them know that if they tried anything I would kill them both before they knew what happened. So #1 tapes #2's hands together behind his back. I have him sit down with crossed legs. Then I forced the other guy to get on his stomach with his hands behind his back. I put my knee heavily on his upper back/neck and I taped his hands together tightly. I then taped his ankles together and taped the ankles of the other guy too.
They swearing at me a bit, but I just remember screaming over them telling them to shut the fuck up and that I wouldn't hesitate to shoot. After they were secure, I called 911 and was told they were on there way. But before that the criminals must've 'slipped' a couple times b/c they were kinda bloody....I was seething with rage and kicked one of them in the face then the kidneys and stepped on the other's neck while I grabbed a half-full Nalgene bottle and took a few swings at his face and his sides. From the moment after I called the authorities to just before they arrived I just remember non-stop yelling at these idiots. I was berating them, threatening them, using all kinds of colorful language, etc.
The cops show up in about 10 minutes and I tell them what happened. They picked them up, cuffed them, and took them away. I was later told that they both had outstanding warrants for several crimes. They were eventually both sentenced to something like 8 and 10 years.
So I guess stopping and apprehending criminals at gun point who wanted to take my property was probably the "most badass" moment of mine.