"Mario-ing" - The act of jumping, usually around corners or while shooting.
"I can't believe that dude tried to Mario me with an assualt rifle."
"Just got a quad from throwing that Pancake at bravo."
"******* (Female dog)" - Bouncing betties. Comes from my USAF days, where the talking flight computer on fighters was called "******* Betty".
"Look at this noob camping with a shock charge and a *****."
"Sneeper Reefles" - Sniper Rifles. I don't know where this came from. Just started saying it.
"Free cookies" - Easy kills like sneaking up behind the enemy and shooting them in the back, or getting a free and easy flag cap in dom, or getting something good out of a CP. This started years ago playing Madden, where we started called easy interceptions free cookies.
Some of my favorites I've heard are from Thunder402. "Dorito chips"=Orbital VSAT/Blackbird, and "C4 Sandwiches" (though I've heard others say that as well.)