LPC is an object oriented programming language that primarily is used for writing muds. The wikipedia entry is a nice read, but there are some points that are really cool that I find very appealing.

The system is started up by a driver. After it has started it accepts connects through telnet, and how it works from here is up to the mudlib. The driver has the capability to destroy and load objects on the fly, so as a programmer you can add new objects while the driver is running, and you can update existing objects and create new instances. If you find a bug you normally won't need to to restart the system, you just fix the bug, load the new object into memory, and everything continues as nothing happened. On the mud that I'm used to, Viking Mud, this is done through a unix like environment.

In this development environment your users (the players of the mud) and you as a programmer share the same platform, and you are connected into the same instance of the game. If you find a bug you may track it, correct it, and if you have coded it well the players won't even notice a thing

As you can see, you are extremely close to your users and they can easily communicate with you giving you instant feedback. And you may monitor them in real time. Programmers heaven