Hardcore Kill Confirmed. I play solo 100% as none of my friends play video games. For this reason I cannot play objective game modes. I keep trying but, ugh. In this game, I like Hardcore because you can use assault rifles and smgs very effectively. Plus, it slows down the 'headless chicken' gameplay (if only slightly). Kill confirmed in BOII allows you to earn higher killstreaks easier as well. You just have to get past the team killing and teammates destroying your equipment.
Either Kill Confirmed, Hardpoint, Domination, or Demolition if the other game modes aren't working well for me. I used to play Demolition all the time in Black Ops, but now it doesn't work too well for with all of the spawn trapping. I Mainly like Dom and KC.