Group Plugin
You can make a group with a name of up to 15 characters with the command /g create [groupname] (without brackets). Only people in your group can build/place, break, and use blocks on your claimed land. You can invite players to join your group, promote them to moderator or even co-leader, and can claim land in the overworld and nether.

Groups start with 10 claims, each comprised of a 16x256x16 Chunk. To claim land, first make a group, then run /g claim. Claims need not be adjacent. Your group gains a claim for each week that it is active.

You can lock certain containers and doors. This makes it so that only you can open them. You can also give individual players access to them. These kinds of blocks can be locked: Doors, chests, hoppers, droppers, and dispensers. To lock a block, look at it and run /g lock. To give another player access to it, look at it and run /g lock add [playername] (without brackets).

Permission Levels:
Groups have a leader [L], moderators [M], and normal members [G]. The leader has access to all group related commands. Moderators have access to claim related commands, inviting and kicking members. Normal members have access to the rest.

Group destruction:
Players are automatically kicked from groups if they do not play on the server at least once within a certain amount of time (currently 28 days). Empty groups are destroyed automatically, losing all their claims. Thus, to keep your claims, we recommend connecting to the server at least once each week.

/findpets - Shows the last known location of your pets.
/sendpet - Teleports a pet to its owner (requires the owner's confirmation)

Dueling lets you fight other players without the risk of death or losing items.
At the end of the duel, you are returned to where you were when the duel started, and your health is restored.
You will not regain any items that you used or consumed during the duel, such as arrows, potions, and food.
You cannot hurt each other during the countdown before the duel or for 15 seconds after the duel ends.
If you attack another creature or player, or if you run away, the other player wins. Thus, do not attack anything other than your opponent.
/challenge This challenges another player to a duel. The person you are challenging will see a prompt to /accept or /decline the duel.
/accept This accepts a challenge. There is a five-second countdown before the duel starts.
/decline Declines a challenge

In-game mail:
/mail read shows new messages
/mail send [playername] mails your message to the player.

/jail [playername] Puts a player in "jail" until an operator can investigate and pass judgement.

The following 'help' commands can be used in game for a list of commands:
/g help 1
/g help 2
/g help 3
/g help 4

All group commands:
Here are the available commands ([L] symbolizes commands available only to group leaders, [L, M] for leaders and moderators):

/g adjustmaxpower - Controls your group's maximum power and power damage
/g autolock [add/remove/public/info/unlock] - Lock several blocks by punching them
/g autolock off - Disable autolock
/g lock - Lock a block that you are looking at. Must be in your group's territory
/g lock add - Give another player access to your locked block
/g lock remove - Revoke a player's access to your locked block
/g lock public - Allow public non-group member access to the lock
/g unlock - Unlock a block you own that you are looking at
/g lock info - Show info about a look that is being looked at
/g chat - Switch chat modes between public chat, and group chat and friend chat
/g claim - Claim the chunk you are in for your group [L, M]
/g show claims - Show a list of your claims in the world [L, M]
/g unclaim - Unclaim the chunk you are in [L, M]
/g unclaim all - Unclaim all land [L, M]
/g unclaim - Unclaim a remote chunk in the world [L, M]
/g create - Create a new group
/g destroy - Destroy your group [L]
/g info [group name] - Show info about your group or another group
/g invite - Invite another player to your group [L, M]
/g friend - Friend another group [L]
/g gm - Set a message for your group members to see upon login[L][M]
/g gm off - Disable message shown to group members upon login[L][M]
/g join - Attempt to join a group
/g kick - Kick a player from your group [L, M]
/g leader - Give another player leadership of your group [L]
/g leave - Leave your group. If you are the only member, the group will be destroyed
/g map - Toggle the in-game map showing your orientation and nearby groups
/g mod - Set a player as a group moderator [L]
/g power - Show a group's current power
/g rename - Rename your group to a new name [L, M]
/g unfriend - Unfriend another group [L]
/g uninvite - Revoke an invitation to a player [L, M]
/g unmod - Revoke moderator status from a group member [L]