One of the new and exciting features of Halo 3 is the Forge. The Forge isn't a typical map editor like you see in many other games. It does not allow you to change anything major in the level such as level geometry. Rather, it allows you to place any weapons, objects, vehicles, spawn points, or tools from Halo 3. For example you could easily place a flamethrower and bubble shield in your base for your teammates to pick up. You have a lot of flexibility in what you can place but you are limited to the amount of objects you can place; there is a cost associated with each object. You have a maximum amount of dollars you can spend to avoid overflowing the memory. Small objects cost less while larger objects such as vehicles cost more.
You can also play Forge with friends allowing you to delete enemy's objects while placing objects for your own team. Up to seven of your friends can join you forming different teams. You can attack each other as well as go into editing mode which turns you into a monitor like Guilty Spark. You can be attacked while in this mode so you need to pay attention to your enemies, but you can drop or move any object you wish. You do have some limitations such as not being able to delete vehicles while people are still in them.
The Forge looks like a great addition to the Halo franchise which should many unique gameplay experiences to our multiplayer games.