I have 2 to share
WARNING: wall of text
Modern Warfare 2, Search and Destroy on Skidrow (or w/e the one with the apartment buildings and the playground is called, it's been a while) 6v6 match, defending for the final round all 5 of my teammates rushed their spawn and managed to kill ONE guy before they all got destroyed leaving me to fight the other 5 alone. One of the other guys started randomly shooting his gun (sounded like a Barrett 50 cal) but he was nowhere near me so figured it either a distraction or a trap and went to go check on A rather than track him down. right as I went in the hallway where A was, I saw someone slip into one of the side rooms, so I walked into the space between the bomb and the door in case it was another trap. right when I got into position, I saw the other guy come back out and shot him through the crack between the bomb site and the wall. I turned to the right just in time to see the enemy bomb carrier attempting to back up into the same spot I was in, so I knifed him, but the lunge put me into the open. I decided to look left and saw another enemy just as he saw me and I barely managed to kill him first (this got me the "Enemy of the State" challenge). I went back into my hole to reload, looking back to the opening in case some one showed up (which, of course, they did). The guy ran by, clearing trying to just pick up the bomb and gtfo, but I knifed him as he went by. The 5th guy never showed up and I wasn't about to risk losing the game to find him (yes, winning IS more important than getting kills so STOP CAMPING THE FLAG AND CAPTURE IT!!!), so the last 1:30 or so were pretty dull. I figure he went into a corner and pissed himself seeing as how I just killed all his remaining teammates within a time-span of about 10 seconds.
BFBC2 Conquest don't remember the name of the map (it's been even longer since I last played BFBC2, it was a desert with one town where all 3 objectives were, one team spawned near a bridge, the other on some outpost on a hill) My squad (which consisted of me and one friend) were inside a house at the end of the main road through town. I was looking out the window to see if anyone was trying to take the CP on the road when I got sniped by a guy on a rock on the other end of the map. I was taking a LOT of shit that day and was already angry, so in my rage I decided to try to snipe him back by going to the same window and shooting at him. In my rage, I ALSO forgot to get out my sniper class and still had my shotgun out, so I switched to my pistol, hit the back button to bring up the red dot and started shooting. I kept hitting him, which stopped him from being able to hit me and after a few seconds he realized that and jumped off the rock trying to run away. A small adjustment to my aiming and a few final shots later, the dot disappeared and I got points for the kill. Then I got points for a headshot. Across the map. With a pistol. Both my friend and I started laughing about it right then and there.