Minecraft - A block-building game that allows you to create and explore entire worlds from scratch.
Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
Terraria - Dig, Fight, Build! The very world is at your fingertips as you fight for survival, fortune, and glory.
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Minetest - Minetest is a near-infinite-world block sandbox game and a game engine, inspired by InfiniMiner...
RescueTime - Time management software that shows you how you spend your time & provides tools to help you be more productive.