When originally concocted this idea was for someone who liked/preferred L5R and as such I'm going to present it in the original format which is why "clan" is used in the setup. For a more traditional sword and sorcery game you can use kingdoms. Alternatively you can use "houses" for a sci-fi empire game like Dune or 40k, or even just countries. Whatever you want, as long as there is a high profile wedding of significance to the world around it.
The groom-to-be is a high ranking samurai of their preferred clan. To end a war with whatever clan best fits the bride-to-be's personality (or, if she games, her favorite clan) a prestigious wedding has been decreed and arranged by the Emperor. The bachelor party attendees get to play a group of bodyguards and escorts provided by the Emperor (freeing them up for their own clans of choice) and have the simple objective of making sure the groom arrives at the wedding on time and healthy. If they fail the war will continue and the Empire may fall into chaos unseen since the days of the Clan Wars.
Forces on both sides do not want the wedding to go through. Ninjas, warriors, and courtiers are dispatched in order to ensure that the groom does not make it to the wedding on time. Some of these are sent by forces within the groom's own clan, and some by the other clans who think they can benefit from the war continuing. The actual challenges should be custom tailored to the group based on who is playing and what clan/role/class they have chosen. There is no point in setting up a lot of combat encounters for a group made of Shugenja and Courtiers while the focus should be on sword play and duels if bushi are present in force.
Important Points to Cover
Some important points to make sure you have covered going into this.
- Party guests should be told that the game, while meant to be fun, is also going to focus heavily on the groom-to-be as it is their party.
- Don't make so many challenges that the game is going to take longer than you have to run
- The idea here is for a fun time, a game that ends with the groom-to-be dead on the side of the road isn't going to be fun. Of course, a game where the groom gets through for free isn't going to be fun either.
- There's no need to actually run to the wedding itself. Just the groom's arrival is a good place to end.
- Feel free to add in-jokes and other personal touches to the game.
Above all, remember that it is a game, a party, and symbolically is the groom-to-be's last chance to spend a night selfishly out with all their friends before they bind their life to another person's and go on to a new phase of their life. Enjoy, and if you run it let me know how it goes.
Obviously, this could just as easily be a Bachelorette Party game as a Bachelor Party game.