So what's your favorite story when you just knew what everyone had? And how did you figure it out?

Mine happened last weekend. 200$ buy-in tournament. 9 handed. Still first level (30min levels). One of the first hands. Everyone sitting at 150-ish BBs (bet sizes will be rough estimates).

UTG raises to 2.5BB
UTG+1 (Hero) looks down at KK and reraises to 8BB (too small, but not important for the story)
MP calls
HJ calls
BB calls
UTG folds.

Flop: AA3 (rainbow)

BB checks
Hero checks (I would check my entire 3-bet range here)
MP bets about 1/3 pot
HJ calls
BB calls
Hero snap folds. I am convinced at this point I'm holding the 4th best hand.

Reasoning:
MP has an ace. He isn't bluffing into 3 people (lots of big aces in heroes preflop 3-bet range who could be sandbagging the flop). On this action/board MP could be holding an ace or pocket 3s but...
HJ has an ace. On his action he could be holding an ace or pocket 3s. He's not setting up to turn a missed hand into a bluff later because he has to assume MP is at least holding an ace (see above) and he's never bluffing him off that but...
BB calls. He must have the pocket 3s. MP wasn't bluffing and HJ isn't either. So if BB were holding an ace he would have to assume someone else is holding the pocket 3s and he's drawing virtually dead and he'd fold. But he calls so BB has the 3s.
I am discounting A3 or other really raggy aces for MP given preflop action. Same (to a lesser extent) for HJ. Due to the 3-bet pre I'm discounting hands like connectors with a 3, 42s or 45s gutshots.

Turn brings a 6 (still rainbow)
MP bets half pot
HJ thinks a long time (seems very uncomfortable) and calls
BB calls

At this point I'm thinking:
MP is making an obvious mistake. He's holding a big ace. Given the action he somehow deludes himself he's ahead. AQ or at least AJ. Probably not AK as he didn't 4bet pre.
HJ makes an even bigger mistake with a smaller ace but obviously not a full house or he would reraise beacuse if he pieced the above together he would get a call by the BB at least.
(Read: I'm discounting A6 for MP and HJ for the same reason as after the flop)

River is a 8
MP downbets to quarter pot.
HJ hems and haws and finally folds
BB shoves
MP groans. Thinks a lot but still ends up calling.

Cards as expected: MP shows AQs; HJ claims to have folded AT; BB tables pocket 3s

There are some stud hands like this in an older 2+2 book, can't remember which one. Where you know exactly what someone's hole cards are based on their actions.
But these only hold true if you are playing with fairly rational players. I don't play many tournaments, but IRL NLH cash games, there is always someone who plays completely bizarre hands preflop even for large raises and who make post-flop plays that make no rational sense.

I mean, kudos to you for being very good at putting players on a hand, but if everyone at your table plays fairly rationally, you're probably not in a very good game.

Well, in tournaments you generally don't get to select who you play against.