I've found the only way to really have fun in this game is to run the riot shield. I've gotten pretty good at judging when an enemy is going to reload or throw a grenade. That's when I switch to the Spas and blow their face off. Then the sweet sweet sound of rage.
Just got the protect and serve emblem last night. I'll be rockin that for awhile, but I still prefer the backsmasher emblem (hee hee, backsmasher).
My loadout...
Riot shield: melee
Spas: grip/focus (ext mags and range aren't unlocked yet)
Claymore
Trophy system
Slieght of hand (faster weapon swap, equipment use, and reload)
Overkill
Steady aim