KSG is my new baby. I was playing the FAL and the MSMC until I unlocked the KSG shotgun this morning. My dad and I were considering purchasing a real life one a few months ago, and to see it on CoD was awesome. I tried it out, and "ONE SHOT KILL FOR DAYZ!!!!!
For real though, try out the KSG. Its a slug, not spread, so remember to ADS when shooting.