Sea Battle Tafl
Sometimes called Longship tafl, sea battle tafl is a modern variant of hnefatafl. It's similar to the Tablut game played on the Brain King web site, with some tweaks applied by Aage Nielsen. Played on a 9x9 board, it gives a very balanced game. Aage reports that on the 11x11 board it gives too much advantage to the attackers, but I think that if the diamond formation of the defenders is swapped for a cross, the game might be as balanced as the 9x9 version. The rules are as follows:
1. The game is played by two players on a board of nine rows of nine squares. One player takes control of a cargo ship and eight defending longships, while the other has sixteen piratical longships approaching to attack. The pieces are laid out as in the diagram.
2. The defending player makes the first move. In each turn a player moves one ship as far as desired along a row or column, taking care not to land on nor jump over other ships.
3. An enemy longship is captured by surrounding it on two opposite sides along a row or column with two friendly longships. The cargo ship is captured by surrounding it on all four sides by attacking longships. The cargo ship is unarmed and cannot assist in capturing enemies.
4. The defending player wins if the cargo ship reaches any square around the edge of the board. The attacking player wins if the cargo ship is captured.
Notice that in this game there are no special squares. Any ship may pass over or land on the central square. It is a very elegant game, in that the rules are few and very simple, and the game appears to be well balanced between players.
You can play sea battle tafl here against the computer, or against other players at Dragonheel's Lair (where it is called longship tafl) and Aage Nielsen's site.