I am scratching my head to come up with “the best”, and unfortunately I don’t have anything to rival some of the great anecdotes here. Very enjoyable thread, btw. But also I have been watching the “best sportsmanship” thread slowly lose ground (in post #) to its evil cousin, the “worst sportsmanship” thread, in the past few days!
So I did have one fairly trivial story from a recent game to share - to try to shift this back to center a bit.
(That said, I have a more entertaining one to post in the evil cousin thread… a little later. So the best I can promise is to not worsen the imbalance.)

Our club, I suspect, is not atypical. We have a nice range of adults in terms of age, skill, and background - for the most part, a pretty social and cordial group (until, of course, the games begin!). And several kids of middle school/junior high age - anchored by a master’s son and his friends - most of which the master either currently gives lessons to, or has recently given lessons to. And unfortunately, virtually no women - but that’s subject for a different thread(s).
Back to the kids. They make up about 20% of our numbers, and for the most part are pretty solid players - with ratings in the D/C groupings (and a couple B); pretty decent for that age span. And as many of you know (and also have the battle scars), these kids are typically on a sharp rating rise slope - with their calculated (fairly, based on cumulative performance) rating often trailing their true, current ability by something like 150-200 points.
Anyway I’m playing one of the youngest - maybe 11 years old - a young man that I had beaten once before, but not easily. And although he’s rated about 300 points below me - once again this night, he’s giving me a battle, really making me work. I am at about move 33 and in real time pressure (maybe about a minute left), and he - like most of these kids - has only used a fraction of his time. (That’s demoralizing in itself - their rising 1300-1400 appears much, much more effortless than my struggling/sagging 1450-1500… oh well.) The point is, in this game I have worked hard (for me) to win a pawn, and now with the endgame approaching, my King position, too, is superior.
So I should win this game. Except… there it is, that da*ned clock. Tick, tick, TICK.
After his move 38 I spot an advantageous Q-check, which I make. It looks like I’ll win another pawn with it, but then I realize I’m mistaken - he interpolates a piece with an attack elsewhere, negating my threat. But still not a problem, except… tick, TICK. 8 seconds; then 4. I grab my Queen and make another move that looks like a logical double attack, but not with check this time. I hit my clock soundly, as it reads: 0:02, indicating move 40. Ahhhh.
At this point I recall (!) that I’ve got a need to get up, long overdue, as I’ve had a couple coffees and water without ‘compensation’ for a couple hours. Having ignored that is now, I realize, physically uncomfortable. I mumble something stupid like, “ah, forty”… and start to get up. But now I see a look in the kid’s eyes that I hadn’t seen before - and it was a bit freightening, halting me in my movement out of my chair. Normally reserved, his eyes were bugging out of his head - and he was unusually animated. With a good balance of excitement and respect, he blurted, “But - you can resign, now.” HUH?!? Instantly it hit me. My King, although on the 7th rank, was effectively on the 8th as it was trapped on a2 behind my a and b pawns (on the 6th) - and he had clear sailing to the 7th and 8th with his Rook and Queen. My double attack was meaningless, as it would be an elementary mate in 2.
I stood up with as much composure as I could muster, but I was very upset - 0% at my opponent; 100% at myself. I had blown a won game on move 40 by inviting an elementary mate, and of course it wasn’t going to be missed. It was the second week in a row that I had made a serious blunder (although this was by far the worse of the two), and I was very upset at myself.
Here was the sportsmanship part. The young man was initially gleeful and of course, happy to cash in the point. In that he did NOT overcelebrate, certainly not for an 11-year old. But then, in about a second and half, he saw and understood my disappointment. His mood changed instantly, as he tried to console me(!). “Don’t feel bad. You had a winning game. You played great, and only lost because you had time trouble.” That attitude, of course, made me feel better about the whole thing and I congratulated the kid in a double measure for his win, and his sportsmanship. After all, I had as much time as he did - I just mismanaged it, which is very much a part of the game. He deserved to win for his better play (including better time management), and I was happy for him - particularly for the remarkable (given his age) compassion in my moment of ‘pain’.
Never happy to lose a point, I could at least really enjoy that young man’s reaction. Of course I related the story to my own kids the next day; my youngest is his age, and I’d hope she’d have a similar reaction to that kind of situation.
Btw, that kid’s rating has continued its climb - and will probably eclipse mine before too long. Good for him.