Armies

Spanning human culture and rife with permutations, the game of Armies is notable for the simplicity of its construction and the complexity of its rules. The board is eight squares by eight squares in a checkered pattern, and six different kinds of pieces are generally the standard. Even if these are called different things in different regions, game shops will have generally accepted replacements, making this game popular for travelers and merchants (particularly those who enjoy bamboozling backwater types with fancy new city rules).
Each major human continent has it's own variation, with additional rules from city to city. Older Sister rules have one player set their pieces in a four by four square in the center of the board (there must be a tower piece on each corner, and the jarl may not be threatened while adjacent to a tower) while the aggressor sets up four rows of four pieces on each edge of the board. This variant is notable for using different pieces on each side, as the attacker foregoes a jarl and towers but has warmachines, while the defender has none of the latter.
Middle Sister's version resembles chess, with only a handful of variant rules. The Republic version of chess treats the two monarchs as equals, restricting one in movement only after the other is defeated. The most popular continental variant is only declaring a winner after both monarchs have been taken.
Younger sister moves the soldiers forward a row on both sides, and adds a pair of warmachines to each side. Notable for allowing players to play captured pieces as mercenaries (and the precise rules for this vary considerably from region to region), cities in Younger Sister see a lot of folks trading or playing for each others' pieces, making this game quite popular among merchants.
The western half of the Great Continent plays mostly by Republic rules, though little variations have crept in, particularly among more rebellious territories. Hisarlik breaks from this tradition firmly, setting pieces on corners rather than within the squares, and utilizing two unique 'zones' that appear on Hisarlik boards (though any board may be used). This version of the game has much more in common with Xiangqi than chess.
The eastern reaches of the Great Continent, the pieces have a firm hierarchy and more complicated boards are complete with traps (this version is most similar to Dou Shou Qi), with the lowest piece set as the humble assassin, who can only defeat the regent, and various types of units in between.