"MingeBag" is the default player name in the HL2 Mod "Garry's Mod" (Now sold as Version 10, Version 9 Is no longer supported)
"MingeBags" were players who either through choice or lack of knowledge did not change their name. They would usually join a server and spam the spawning of large objects often crashing servers. However prop limiters prevent this nowadays. They would also destroy or interfere with other players creations.
Pontus, "Notorious, world-known gmod comic maker extraordinaire." was quoted: "Moron with a zero-point energy manipulator attached to groinal area"
These people, are of two "Classes" the generally innocent newbies (see "newbie") and those who are out to ruin the fun of everyone else.
Generally there is no time to tell the differences between the two and rivalries occur between players and "MingeBags" resulting in the server becoming a Deathmatch.
Example: Go play garry's mod and join a server under the name "MingeBag"
"OMG ITS MINGEBAG BAN BAN!!11"
"Here, Wanna help me build a fort? I help MingeBags :)"