TwixT
Players: Two
The players try to link their dots to form a continuous chain from one side of the board to the other.
Description
The board
The game is played on a large grid of dots, at least 12 x 12, excluding the four corner dots. One player uses a blue pen and the other uses a red pen.
The top and bottom rows belong to blue, and the leftmost and rightmost columns belong to red:

Blue plays first, and the players take turns in marking a dot anywhere on the grid, apart from on their opponent's border.
Linking dots
After placing a dot a player can optionally link a pair of their own dots that are a knight's move apart; in other words, one dot apart in one direction and two dots apart in the other direction.
A player's link can cross one of their own links but not one of their opponent's. Links that cross aren't considered connected.
The first player to create a continuous chain of linked pegs connecting their border rows wins the game.
Variations
You can use the Pie rule to overcome the advantage of being the first player.
Example
Here's an example game in which blue has won:
