StrategyWiki has more information about MapleStory Minigames
There are various minigames that one can play, both solo and multi-player: Omok, Match Cards, Pachinko, Gachapon, Rock Paper Scissors, and Fishing System.

Omok is the Korean cognate of the Japanese game "Gomoku". Omok is akin to tic-tac-toe. To win, a player needs to place 5 of their pieces in a horizontal, vertical or diagonal line.
Match Cards is also known as "Concentration". Match Card games can be opened in grids of 3x4, 4x5, and 5x6 cards. The facedown side of the cards contains images of various monsters, which players take turns matching.

Players having a Maple Minigame (Match Cards 5x6).Pachinko is a mini-game exclusive to JapanMS and TaiwanMS. Pachinko balls may be purchased in the Cash Shop and are required in order to play. The player must be in a Pachinko House to play the game. In order to win, one needs to get the Pachinko balls in a mushroom hole below a slot. Once it is in, the slot will start. If the player obtains a certain amount of balls, he or she may win in-game prizes.
Gachapon is a slots minigame, in which the player inserts a ticket and a random prize comes out. To play Gachapon, one must first purchase a Gachapon Ticket from the Cash Shop. The Gachapon machines are located in various towns.
Rock Paper Scissors is a one-player minigame based on the actual game, in which one plays against an NPC.
Fishing King is currently available in TaiwanMS[13] and ThailandMS[14]. The player can complete a quest to obtain a diving suit before being sent to a map that resembles an Aqua Road map to catch fish. After the player has acquired a diving suit once, the player may return to catch fish as many times as they want to.
The Fishing System is currently available in all versions except KoreaMS, (NA)GlobalMS and EuropeMS. Players can buy fishing equipment (fishing rod, fishing chair, etc.) from the Cash Shop and talk to an NPC in various towns to go fishing.