Anti Martyr
When you're next to a fresh drop Martyrdom grenade pick it up and toss. Its got a fuse that lets it be an effective grenade and if you get a kill it looks like you're a pro who knows what he's doing. Best done after a knife kill or something else that close. Grasious Guns
The M21, G3, M41 and R700 use the same ammo. Using overkill with any four of these will let them share ammo giving the meager R700 an extra 40 rounds to use but also using the other weapon will drain the stock for both. My favorite combo is the M21 and a G3 with red dot sight and bandoleer. its hard to waste all that ammo when camping a good spot. Sharing Ammo
A lot of other guns share ammo. I think the M16 and M4 do as well as the SAW and the other LMG's but I've only confirmed that with snipers. The Domino Effect
A good trick for Domino or just getting a fun kill is to set up a claymore facing a car slightly backed away then face another claymore at the other one and towards the street. When they run past the car the claymore will set off then detonate the other one then that one will set off the car making a large chain reaction and almost historic kill. Pink Mist
When fighting just know that the spray of blood lets you know you go a kill. If your on hardcore or in story mode know that if you shoot and there's no blood they aren't dead. This can leave the target to use the last stand perk while you turn and walk away. Whos There?
When you're sniping a claymore is as good as someone ringing your door bell. Since most camping spots only let you in two ways, setting up a claymore at each entrance lets you know where they are so you can ambush or run away. If you run past your claymore they may follow. Choper Inbound
When a helicopter is out and about its going to kill the one with the most kills or points. If your him or close to it get out of sight. take it down and remember its got like infrared so hide under something with a solid roof. GTFO HELI!
The rocket is basically crap. No accuracy and a smoke trail. The best use for taking down a chopper is a mounted machine gun or an LMG though i've taken one down with a pistol and determination. From Behind
On the back lot map (I think that's the name. It's the one with the two story building in the center that you can climb on the roof) move into the building with no walls but the back and partial sides. An easy camp spot is at the bottom of the stair well. When people run past to go to the top floor with the mounted machine gun, you can run up behind them and knife, shotgun or if your good head shot. The funny thing is if your on the radar they think your at the top so they slow down and move up slowly, and when you run around behind them it looks like your running away up top.