Economic Simulation: "Beat Japan"
I designed this simulation for an 11th grade Economics teacher. Students took the role of auto company CEOs, applying investment strategies in competition with each other (and, to their increasing surprise, Japan, which played by very different rules). Every morning they would read a news blog, meet as teams, and take new actions; the teacher would respond by creating the next morning's news blog, and informing each team of its financial status.
I include this because I was deeply involved in role-playing games as a teen and young adult (Dungeons and Dragons). Computer-based RPGs are not in the same league, because of how they constrain the imagination with visual imagery. I consider training the imagination to develop a provisional interactive space with evolving roles and rules to be a very powerful instructional technique.