Not very impressive, but mine is 36. It was at the Pentagon (a level where I always lose). It was near/far. I basically camped in the building with the SR, on the opponents' end. I primarily used the SR. (having to reload probably helped me avoid defensive problems)
The best part was YOUKNOW! was on the opposing team for around 20 of it.
My best kill streak was 18 kills in Warehouse with only a pistol and grenades. I don't play enough because of hackers but hey, it was enough to make everybody rage quit. :/ I lost all my stats from that game.