I'll show mine

Any snapback, however small.
Monkey jump & big monkey.
Cranes nest, which I can only spot in its more simple form.

Any situations that are more complex are usually the result of reading out a formation with which I have previous experience; not so much tesuji as patience and careful setup. A good thrill.

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David Bogie, Boise ID
I play go, I ride a recumbent, of course I use Macintosh.

I've always really liked ladders. The two that gave me the biggest "oh, that's cute" moments when I came across them first were the loose ladder and the double ladder. Not for being very complex or anything, I just really enjoyed the logic of them. Oiotoshi (Connect and die) was another like this.

I like tesuji that show me that there is more to Go than counting liberties, like the raccoon's belly, and playing to get a hanezeki.

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A good system naturally covers all corner cases without further effort.

I like, among the simple ones, the warikomi.

Knotwilg, you should like this problem then: https://www.lifein19x19.com/viewtopic.php?f=15&t=5099

As for my favourite tesuji, patting the tanuki's belly is probably my favourite standard one. Although I have played it in real games a few times I've yet to actually win because of it: once against Nick Krempel it was actually bad and simple outside block worked better and didn't get squeezed, another time against Junnan Jiang (the year he won British championship) it was a fight winning tesuji (which I had spotted before starting the fight, yay!) so I was then leading but messed up later.

Other shortlisted ones are the double ladder breaker and under the stones (a favourite occurrence being all 3 of us in a London Open rengo finding it).

And for famous historical tesujis, Shuei's running out of a net.

I like this one, too. I have memories of trying to solve a go problem where this was the solution - I hadn't seen it before. I spent a really long time before finding it. I kept reading the same sequences, and skipping this tesuji, since I kept overlooking it.

Generally speaking, I like tesuji that are surprising to me more than standard ones. Particularly if it helps in making some sort of comeback from a lost game.

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be immersed

I don't know about favorites, but I think it's kind of amazing that can be the best move (T5 also works, but nothing else does).

Click Here To Show Diagram Code

[go]$$Wc Threat of a threat
$$ ---------------------------------------
$$ | . . X O O X . . X X X . X . X O C 1 X |
$$ | O X O O X X . X X X O X . X X O O X X |
$$ | O . X O O X X . X O O O X X . X O . . |
$$ | . O O O X X . . X O . O . X X X O O O |
$$ | O O O X X . X . X O O X X X O O X O X |
$$ | X X X O O X X X O . . O X O O X X O X |
$$ | . . . O X X O X O . O O X O O X X X X |
$$ | . O O O O X O O O O . . O O O X . . . |
$$ | O O X O O O X O . . . O . X O X . . . |
$$ | X O X X O . X . . , . O O O X , X O X |
$$ | X X X O O . . . . . X O X X X X X X X |
$$ | . X O O . . . . . . O X X . X O X O X |
$$ | . X X O O O . . X O O O X X O O O O X |
$$ | X . X X O . O O O O O X X X O O . O O |
$$ | . X O O O O . . O O X . . X X X O 2 . |
$$ | X . X O X X O O . O X . . . X O O O . |
$$ | . . X O O X X O O X X X . . X X O . . |
$$ | X X X X O X X O X X . X . . X X X O . |
$$ | . . . X O X X X X X X . . . . X O O . |
$$ ---------------------------------------[/go]

*cough* "Do you smell smoke?"

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Help make L19 more organized. Make an index: https://lifein19x19.com/viewtopic.php?f=14&t=5207

Strange indeed. White can't connect the ko immediately, and if White ever plays at S17 or T17 then Black takes the ko, White is in atari and has no ko threats, so loses the ko.

In addition, if needed Black had real ko threats at B17 or M12 (atari).

Black absolutely needs the real ko threats at B17 and M12. If black didn't have them, then white would win easily.

Basically, why must black specifically play at S5 or T5, and no other move wins? Because even though the move is not itself a threat, it threatens a future ko threat, and that's what's needed in this situation.

If black plays S5, then:
* White protects B17 or M12.
* Black takes the ko.
* White protects the other of B17 or M12.
* Black now has T5 as one final ko threat, so black escalates the ko to be for white's whole group, with S17 or T17.
* White takes the ko.
* Black plays T5, white responds.
* Black takes the ko. White has no threats, so white loses the whole group, which is enough for black to win.

If black were to play a dame or any other move (including B17 or M12) instead, then:
* White protects B17 or M12.
* Black takes the ko.
* White protects the other of B17 or M12.
* Black has no threats left, so black can only connect the upper right ko, getting a seki, which is not enough to win.

----------------
So when there is a thousand year ko involved, you may want to play moves that are dead in gote in the opponent's territory, simply because in the *future* it makes a threat. And you want to play moves in your own territory that add extra defense to groups that are already alive, simply to reduce your opponent's future ko threats.

Extra details:

Thanks for the detailed explanations. I didn't realize that in the sequence "If black were to play a dame or any other move (...)", if Black doesn't want to connect the ko nor to play S17/T17, White can leave the ko unsettled as well and the position becomes a seki.

Here are two problem positions I rather like. Black to play.

Click Here To Show Diagram Code

[go]$$Bc19
$$-----------------------+
$$ . . . . . O O . . . . |
$$ . . O X X O X O . . . |
$$ . . O . X O X O O . . |
$$ . . . O X X X X O X . |
$$ . . . O . X . X X O . |
$$ . . . . O X X X O O . |
$$ . . . . . O O O O . . |
$$ . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code

[go]$$Bc19
$$ . . . . . . . . . . .
$$ . . . O O O O . . . .
$$ . . O X X X O . . . .
$$ . . O X . X O . . . .
$$ . O O X X X X O . . .
$$ . O X X O O X O . . .
$$ . O . . O X X O . O .
$$ . O X O . O X X O . .
$$ . . . . . . . . . . .
$$----------------------[/go]

The tombstone squeeze is another favourite.