First off, I was playing against some dude that had Orbital VSAT, K9 Unit, and Swarm and got it in all 3 matches we played (against pretty decent competition, we were all at least level 1-4 prestige). He must have known what he was doing, because while he was good, he didn't strike me as an exceptionally skilled player (I figure I killed him more times than he killed me in "head-to-heads"). He went essentially 55-15 every round. The matches were even till he hit those scorestreaks, then his team would pull ahead (it was Kill Confirmed).
For me though, I think my most kills was like 58-8, my least deaths was like 24-1 (with the last death coming literally seconds before the match ended as I was haphazardly running around the map).
My best match though was probably against almost exclusively level 4 prestiges and up (I believe some were in a clan) where I led my random team at like 36-12 calling in (what I thought) was the gamechanging Orbital VSAT near the end for a narrow 100-99 win :)
In general though, my favorite matches are where I'm lucky enough to call multiple Sentries, Dragonfires, A.G.R.'s, Orbital VSATs, and/or Stealth Helicopters (I don't usually run the big dogs like K9, Warthog, or Lodestar unless I feel like my competition is really beneath me and I'm feeling lucky). Those matches for me are about 35-10.
My best match was on Meltdown TDM with the S12, I went 24-2 and we still lost! A couple guys on my team were really awful. One went 0-13 for example. But I used the lightning strike and only got one kill, used the Dragonfire and got like 4 kills with that. One time I died because I ran out of ammo and picked up a semi-auto rifle and didn't realize it wasn't auto fire. So I went to shoot someone and they got me easily.
Playstation 3 owner. An average Call of Duty player.