Lol minigun. I tried it online and offline. Offline = Pwn at close range. Online = Crappy piece of junk even against Zombie Bots.
Now I personally like to use either the AK or the Minimi because they have good damage and higher ammo clip than 30. As for the AK, I prefer it cause it reloads faster, and Minimi I prefer it because it has a faster bullet speed
Aug... well it's not really to my taste. Damage is a little low for me and I think it fires a little too fast for my personal style of gameplay.
Funny, the first auto(and weapon) I used seriously for a long period of time was the AK. Second auto is Aug, third auto which is now, the Minimi. Sometimes I may jump between with the AK.
MP5 is too fast, too low damage per shot and too low bullet speed for my liking (which is basically almost every reason why people use MP5 lol!).