I have 2 from which i can't decide.
The first one requires some back story.
My parents are dealing with a tricky divorce, my father and sister both have strong autism, while me and my mum are very reserved, much like BenD i guess. I've never lost my temper, save this occasion (and one other time which, while is a pretty cool story, wasn't very tense).
It was a Wednesday around 6PM, and on the thursday i have an EEG. It's essentially a brain scan with various flashing lights and stimuli, for which i have to be sleep deprived. So that night i had to stay awake all night, while my whole family live together despite a very awkward divorce. Stresses were high and my dad was at boiling point.
Me, my mum and my sister were sitting at the dinner table, just eating a dinner as usual, when out of the blue my dad storms in banging around and shouting. Ranting about how he didn't deserve any of the supposed shit he was getting. By this he meant we weren't chatting to him like we normally would, surely an understandable side affect?
So yeah, he was shouting, banging stuff, making a lot of noise and making accusations about my mum and sister.
I couldn't bare it, no-one was saying anything, as in none of me, my mum and sister.
So i stood up, and shouted "shut the fuck up and get the hell out". Not only the first time shouting at the top of my lungs, but the first time i'd swore in front of my parents.
I guess it doesn't sound like a big deal when relaying the story, but at the time it felt huge.
Suddenly after that everything fell silent save the cutlery i'd thrown across the room at a window. I was standing, haunched over the table, and decided i'd had enough, and so i finally threw my chair across the room (more of a strong barge) and left. Just ran.
Felt good to let everything out of my system and i'd finally calmed down.
It feels weird even typing about it, may not sound very intense but it finally made my dad see i had a spine and i think i earned some respect from it.
tl;dr
SHUT THE FUCK UP AND GET OUT
the other story is thankfully somewhat shorter.
I was ill when i was around 7 with pneumococcal septicaemia. I was in hospital for a week or so and was in a coma for a few days in a critcal condition.
It was spreading to my brain so it caused hallucinations. Those were pretty intense...
The only one i really remember was that my room felt like a battlefield. Gunshots blazing all around, really surreal.
First stories better imo.