Gomoku
Gomoku, also called "Five in a Row", is an abstract strategy board game. It is traditionally played with Go pieces (black and white stones) on a Go board, using 15×15 of the 19×19 grid intersections. Because pieces are not moved or removed from the board, Gomoku may also be played as a paper-and-pencil game. The game is known in several countries under different names.
Irensei
There are two restrictions on this: (1) A line of seven stones which covers any point on the outer two lines of the board is not a win, and (2) Black cannot make a line of eight or more stones. However, when a group of stones is enclosed by the enemy as by the Go rules, the stones are removed (remember that diagonal is not considered a connection for capturing but is considered a connection for a win). Also, the suicide and Ko rules apply, and indeed are often crucial in winning the game.