Not a bad beat story. More a pwned one. Not really life-changing either, but the one I learned most from, so the most helpful to my time playing poker.
First time I'm in Vegas. 2008. Staying and mainly playing at Flamingo in the softest $1/$2 game around. Even I'm winning in it. My friend and I were essentially playing in the morning, making a few quid and then going to Caesar's to play the Deep stack event that day.
It's Day 1B of the Main Event but I'm happy to sit on a furry pink table with some middle aged people in braces and those glasses that have folding sunglass-lenses. That said, we've built a fun table and everyone's having a laugh. To my right is one Wayne "Hawaii 501" Mardle and we're sharing Spurs stories and being token Brits.
I'm also building a nice stack. There's a chap two to my left who I know only as "Bubba". He was a portly, ebullient fellow, with a North Florida drawl and a shirt so loud it interrupted any conversation within a hundred yards. He was betting blind, raising dark, calling for a laugh, buying drinks, pulling hundreds from a wedge, buying more drinks, bluffing twenty six streets and showing air, stacking, losing and being a comedy ledge. Not a moment of negativity embraced the table for five hours. Apart from the odd felted nit, everyone stayed and we had the most fabulous time.
I raise the button to $6 with

, playing about $600. Bubba tells me he folded a big blind back in 1982 and regretted it ever since. He calls.
Flop

Bubba looks at me and continues the banter we've been having. "That looks like my kind of flop!" He bets $25. I think and make it $70. He sticks his stack in, making it all in for me to call.
I haven't played a >1k pot before and I'm sweating like a horse in a PrittStick factory. I ask him what I should do (seems only polite to ask...). He says "Depends what y'all have".
He is beaming like a Cheshire cat (or whatever the Florida equivalent of them is - a Marlin?) and his body language and demeanour have not changed one iota. I'm getting nothing.
"You got a pair?" He asks me, as I dwell.
"Am I allowed to tell you?" I smirk
"You can tell me what you like. My money's in the middle!"
We're still laughing. No one at the table minds the time this is taking, and everyone's enjoying the banter.
"So...you got a pair?"
"I might have", I venture
Bubba looked down with a knowing smile and uttered the words I'll never forget...
"Well, I've got outs"
With that, I decided to call. The biggest decision of my poker life to that date. £400 of my own money bet on a single comment. What a hero.
He flips over

for the straight flush.
It was Steve McQueen being schooled by Edward G Robinson.
To make matters worse (yes, as I reached for more money...), Wayne Mardle turns to me and says "That was a really bad call without the ace of diamonds".
My head was a complete mess as the magnitude of the mistake I'd made began to sink in. Bubba was an absolute pleasure to play with, he was playing the main event the following day and I shook his hand as genuinely and earnestly as I have anyone else's.
He taught me a lesson that day I'll never forget.
Great post.