You don't need a router. If you set the subnet mask on all of the PCs to be 255.255.0.0, then they should all be able to ping each other. Basically, opening up the subnet mask puts all of the PCs on ...
One of the best ways to do this is by setting up a Local Area Network (LAN) party over Wi-Fi. Not everyone these days has time to set up Ethernet cables, so using Wi-Fi is much easier and less ...