It can be from any video game, and from any game :)
#1
Team Magma from Pokemon. I originally played Sapphire when I was a kid and just felt so happy that Maxie helped (somewhat) with stopping Team Aqua. I loved their uniforms too.
2points
#2
probably the Stormcloaks from TES Skyrim
2points
#3
My favorite has to either be The Enclave or the NCR (New California Republic) from the Fallout series
1point