Kroot Conga Line
The Kroot Conga Line was a famous lulzy game in a 40k tournament in which a White Scars player found himself shut down and "destroyed" in his first turn by a single squad of Kroot Warriors. While similar tactics were commonplace at the time with Orks, taking things to the extreme of tabling your opponent by deploying in such a public event was unprecidented and attached a stigma of WIN to the Kroot to this day.
The White Scars player was running this in 5th edition, which means he was running under Matt Ward's rules. We can set aside our usual bitching though because the crunch in the White Scars rules wasn't half-bad.
The tournament had a "no named characters" rule for whatever reason, forcing the White Scars player to have Kor'sarro Khan count as a generic biker Captain. While this meant he could still run Bike Squads as troops (fulfilling the mandatory Troops choices in the classic Force Organization charts), it meant his -army consisting entirely of bike squads and attack bike squads- no longer had the Scout and Outflank rules. Undaunted he ran the entire tournament with a Null Deployment strategy anyway, since fast units arriving from reserve still kick ass. Basically he'd been kicking everyone's ass left and right, Khan or no Khan, because 24 bikes and 9 attack bikes put out a lot of dakka and Null Deployment kept him safe from his opponent's first round of shooting.
The Tau player's list has been lost to history. All that's known for certain is that he had a squad of 30 Kroot Warriors. Normally these were useful to have around when you need to screen your opponent's reserves and deep strikes. As we know, they would go on to win this game by themselves.
The Moment of Glory
The board was a standard 60-by-48 inches large tabletop.
The White Scars player kept everything in reserve. Unlike 6th edition, this wouldn't instantly kill him by itself, that rule didn't exist yet, so he could still take his first turn with nothing on the board.
The Tau deployment didn't take long either. The Kroot, using their Infiltrate rule, deployed inside the White Scars deployment zone. Normally they're restricted from deploying within 12 inches of the enemy, but with no enemies actually deployed on the entire board there was nothing stopping 30 Kroot Warriors from running up to the enemy's table edge if they so desired.
After stringing his Kroot along the White Scars' table edge (not hard with 30 Kroot in 2-inch unit coherency), legend says he ended his turn and declared himself the winner of the game. Without Khan's Scout and Outflank rules, the White Scars could only come in from Reserve by the unpopular "walk on" method. But since walk on follows the rules of normal unit movement, i.e. not allowed to cross within 1 inch of enemy models, and with his entire table edge covered in Kroot, there was nowhere on the board the White Scars could actually walk on from.
The White Scars player flagged down a judge, and together they poured through the rulebook, looking for some kind of out that would let the White Scars actually play. Legend says the judges were sick and tired of this guy anyway, but it hardly matters. The Tau were winners by default, as the White Scars couldn't take any turns, contest any objectives, or battle and kill any Tau.
The battle became famous on the interwebz, passed around forums and Reddit, and used as the butt of jokes and "hey check out this cool Tau tactic!" in Tau list articles (such as our very own). It's believed that it even influenced the 6th edition rulebook, when they added in the rules mandating players to start with half their army on the board, though that was more likely to nerf reserve spam lists.