I think the obvious one is Tournaments. Maybe you can have a sign up area that will pull the player back once a time limit for sign ups has been reached or a player limit has been reached so long as a minimum amount of players for the tournament has been met. You can have same "class" tournaments and any "class" tournaments. You can have Non-Elemental only and Elemental only. Also ofcourse having a sign or something that can show a leaderboard maybe every 3 months on who has performed the best in recent events just to keep it spicy for competition. Rewards could easily be distributed based on why type of tournament is being contended in. Ryo, Jutsu scroll, Rare Gear, Rare consumable, and so on.