TacTix is a two-player strategy game invented by Piet Hein. It is essentially a two-dimensional version of Nim. Players alternate taking pieces away from a square (or rectangular) grid, as many contiguous pieces as desired from a single row or column. The player who takes the last piece loses (misère play convention).
The hexagonal variation of the game, played on a six by six by six board, is called TacTex.
On the 4 × 4 grid originally proposed by Hein, the second player will always win with correct play (HAKMEM item #74).
If the game is instead played with the normal play convention (player who takes the last piece wins), the second player can always win by symmetrically mirroring the first player's moves. (Or on an odd × odd size grid, the first player can win by choosing the center piece and subsequently mirroring.)