Two projects in one so far: to learn foreign words and read books
Find as much words you can in a schema (game console based).
A set of Forge mods for Minecraft. (API, Stargate, custom signs...)
A battle engine for a strategic computer game
MultiLingual Interactive Fiction
Quiz Game SWT
Board game Mondrago for Android platform.
Java client for TradeWars 2002
CoffeeMudForAI is plaform to design AI in
An extensible development framework for roleplay games.
DiaT is a Textadventure
A java-based, purely object-oriented chess engine.
Unless you're getting started in Java, you probably don't want this.
Modular Minecraft server plugin - commands, events, ...
A multiplayer First-Person-Shooter game built in Java 3D
An 8 bit emulator created on the scratch, including an assembler.
Java Game, Simple 2d, for Practice and Examples
A Java Tic Tac Toe Game