The first and the only "one key" challenge so far was held in QBasic News forum from 22.10. till 28.11 in the year 2003. The main idea was to create a game restricted to one in-game control key in QBasic. Voting lasted for 12 days in a form of a poll. On this page you can check the rules, all the entries with screenshots and downloads, the voting results and some stuff about the future of this challenge.
Challenge was started and managed by me, Lachie Dazdarian.