Have you seen the millions of other party chat plugins, but not been satisfied with their features? Well, maybe this one will finally quench your hunger. You can have multiple parties, created and managed with labeled GUI controls, each member with a rank within their party, and party persistence across relogs and restarts. There's also optional shared inventories, toggleable TP per party and per member, and more!
KataParty was made by special request for Minecraft user Katatunka.
Coming to v1.2.x, refactored code and all messages are fully translatable, as well as settings in a config file!
Players with the KataParty.create permission can create parties with /kpcreate [name] - after using the command, they will be presented with a GUI:

Each item is labeled and has lore to describe how to use it.
Once the party is created, the creator automatically as admin permissions within the party (not within the server). The creation of the party can be cancelled by closing the inventory screen. Parties are forced to have unique names. The default settings for a party are configurable.
Within parties, there are three ranks: Member, Moderator, and Admin. Party ranks control which settings can be changed and which actions can be performed within a party. As you would guess, an Admin has full privileges, a Moderators have less, and Members have the least. All ranks are still limited by plugin permissions.
A player with the KataParty.manage permission can access the management screen for their party - members of all ranks can access the management screen, but the option they have depend on their party rank and server permissions.

Each item is labeled and has lore to describe how to use it. Players with KataParty.admin have full access to everything regardless of whether they are in the party or what rank they have in the party.
From the management GUI, clicking the player head will open a GUI with player heads for each player in the party, even players who are offline. An admin can left click to increase rank or right click to decrease rank, and an admin or moderator can right click on a member with the Member rank to kick them from the party. The first item in the GUI will always be a name tag which, when clicked, will return you to the party management GUI.
Players with the KataParty.list permission can use the /kplist command to bring up a GUI with a list of existing parties:

Each item represents a party - the item name is the party name and the lore show information about how many players are in the party as well as the names of players in the party. Name tags are public parties which are visible to everyone, whereas papers are hidden parties and are only visible to players with the KataParty.seehidden permission. Clicking an item will have you join the party, but you will leave any party you are currently in as you can only be in one party at a time.
Players with the KataParty.teleport.do permission can use the /kptp command to bring up a GUI with a list of players in their party, even offline players. Each item is a player head named after the party member it represents, and show information about the member's rank, online status, dead or alive, and whether or not that member allows teleportation. Clicking an item will teleport you to that player if that player has teleportation enabled.
Being in a party means messages you send will only be visible to other party members. The chat messages will be prefixed with your party's name. Messages in the global chat will be greyed and italic. To send a message to global chat, start your message with an exclamation point! You can calso use the /kptoggle command to swap chat filtering - party chat will be greyed and italic whereas global chat will be normal, and your messages will go to normal chat by default. Start messages with an exclamation point to send to party chat instead! Or, use /kptoggle again.
When you log in and are already in a party, you will default to speaking in global chat for greetings and such. This behavior as well as the exclamation point are configurable.
If enabled in the party settings, party members with the KataParty.inventory.use permission can access a shared 4-row inventory with the /kpshare command. If the inventory is later disabled or the party disbanded, the person who did so will have the items dropped at their feet.
Important: Only give the KataParty.inventory.enable permission to trusted users, otherwise it could be abused by creating as many parties with shared inventories as they like and be able to use them all like ender chests.
While players can only be in one party at a time, they can freely log off and remain in the party. Parties also persist across server restarts and are saved in /plugins/KataParty/parties.yml - this plugin uses UUIDs for everything so it is safe for when Mojang will allow changing Minecraft usernames.
When players in a party have tamed wolves and PvP is disabled, wolves will not target or attack other members of the player's party. If wolves are attacking a party member and PvP is then disabled, they will stop trying to attack. Additionally, other party members cannot attack your tamed wolves with PvP disabled (but you can still attack them yourself if you need to).
KataParty was originally designed to intentionally not have an invite feature due to server mods and admins complaining about invites being a nuisance with other party plugins. Witch tickets however, you can get similar functionality without the annoyance. For invite-only parties, party admins can generate tickets (special name tag items) that they can physically give to the people they want to invite. Players given a ticket can right-click to accept the invitation and join the party, or they can drop the ticket from their inventory (destroying the item) to reject it. When delivering tickets players have to be careful not to give it to the wrong person. Tickets cannot be used as normal name tags or stored in inventories.
These features are planned to be in a future version of the plugin.
Using the stick button in the creation or management GUI, players can make their party stick around with no one in it if the plugin is configured to normally remove empty parties. Will require the KataParty.stick permission.
Coming to KataParty 1.3.x will be a full API for plugin developers. With the API, your plugin can add new kinds of parties and party members, and you will also be able to allow invitation tickets to be placed in your special inventories. The API is being heavily worked on and may have breaking changes during the first few releases.
When PvP is disabled in a party, splash potions with negative effects will not affect other members of the same party. This means party members can heal and buff each other, and only harm and debuff players not in their party. Additionally, with PvP disabled, team-only buffing can be enabled so that splash potions with positive effects do not affect players not on your team.
Mutually exclusive from PvP, when this option is enabled all players will share the same health based on the number of online alive players in the party. All members will see health drop as any member takes damage. Once the health reach zero, the entire party dies. (Death message collapsing is planned to show a death message for just the party and not every player). Additionally, as any party member gains experience, it is split evenly among all online living party members.
Aside from the parties.yml file which is used for party persistence across restarts, there is a separate config.yml file. This configuration file is smart - if you remove a config setting from the file, on next reload it will be added back with the default value, while leaving your other settings as they are. All settings are documented in the config, and things you can configure include:
NOTICE: The plugin is written in Java 7, and as such, your server will need to run Java 7.
To implement chat filtering, this plugin listens to AsyncPlayerChatEvent with the highest priority (to be processed last), cancels the event, and then manually sends chat messages to the console and to individual players. It respects the target set and message formatting as well as display names. If you have issues with chat filtering, please tell me what other plugins you are using.