I suppose I sort of did, although the actual bit where someone's life was in danger wasn't really saved by me. I don't normally mention it to be honest, and it was a pretty long while ago (maybe a year and a half now

), but since you asked...
Basically, I'd been at a gig in town and was walking back home (bear in mind this is Leeds, in the UK, which isn't a large city anyway and my flat was right by the uni, about twenty minutes walk from the city centre). While walking, I decided to stop in Subway, and due to reading the Shortlist magazine in there I was actually there for over an hour. Leaving, I carried on my walk home and noticed a girl and guy arguing outside. This was notable because I actually recognised the girl - she'd been at the gig as well, and had been acting pretty oddly (i.e. she'd been dancing around, full of energy, whereas the rest of the crowd including myself were a lot calmer - sort of 'hipster' dancing rather than proper dancing, if you know what I mean by that...), and flirting with several guys including myself. To be honest, I had every reason to suspect that she was high.
So yeah, this girl was there, arguing with her apparent boyfriend, and stumbling away, falling over every few metres in the road (fortunately there were no cars about) and pickig herself up and carrying on. Her boyfriend gave up trying to follow her and walkedaway, but I decided to follow at a safe distance until I was sure she was okay. She had blood on her, which I think was from the constant falling over, and was in a lot of distress. I followed her a short way until a group of girls on a night out tried to take care of her, but after hanging around for a bit I noticed she'd left them and carried on alone again. Eventually I ended up following her to a bridge over an expressway (freeway to you Americans) right next to the university.
At this point, I was some distance away, watching, and I saw her climb up onto the railing as if she was going to jump. I was actually scared to walk closer in case she got scared and decided to jump, so I just got my phone out ready to call 999 straight away if she did jump. Fortunately, after a tense moment, she decided to climb back to safety and carry on walking, still crying and in obvious distress. At this point, another guy walking nearby had seen her, and we effectively joined up - I phoned the police anyway to come and pick her up and look after her, and a couple in a car nearby had also noticed her and called the police. They were quick to arrive, we managed to keep track of the girl and when we were in a safer place (i.e. no bridge of death nearby) on campus we approached her, me and this other guy, and tried to keep her calm (a tough job, but the operator had asked us to while the police were on their way). Two officers came, along with a university security guard who'd spotted us, and they took over. I had to give a statement on all the events of the night leading up to then, and as far as I'm aware they got her home safely, but I honestly don't know. Never found out anything more about what happened since then, I just went home and expected a phone call within a few days asking for another statement which never actually came

.
Still, I just reckon that I had to do something, since if I'd been watching the news the next day and seen something about this girl (in an alternate reality where I didn't follow her, creepy as following her may sound) dying in an accident or being a rape victim or worse, I would have never forgiven myself

.