Actually that does work (the SMG thing).
I simply refuse to use a shotgun, so I just chase them around with SMGs, most effective if you think more like a fighter jet, less like a soldier biggrin:


Funniest encounter I've ever had with a shotgun N00B (no this guy really was a n00b):
I was sniper and ran into the guy on snowy park, he starts blasting away as I pull out pistol, he misses all 5 shots (well, not totally but damage is not too severe) and when he's reloading *pop, pop, pop*, dead.