#3 Matchmaking and/or Server List

Gamecraft has some support for multiplayer gameplay, but it's pretty hard to connect to another user's game, since you have to type in their SteamID to the in-game command line. A matchmaking system would be a good way to join other players in a game for doing something specific that everyone wants to start (like play a mock-Robocraft game). A publicly-visible server list would allow players to join existing games (like Minecraft), and see what others are doing. This could benefit from being accessible outside of the game, like on a website.