In my software development class, we worked in a group of four people and created a command line based game where you could move through rooms, pick up items, and fight enemies.
Subnetting a network
I was able to configure an online subnet between different servers, computers, and routers. Each end device was able to ping to devices set up inside their own subnet and I was able to restrict access between certain subnets as well.
Security Competition
Although this isn't necessarily a project, I worked with a group of people at our school to prevent a red team from infiltrating a group of websites and servers in a semi-controlled environment