"Spiral of death" = "circle strafing", a time honored first person shooter technique, here is a summary, from Quake, but applies to pretty much all FPS so far:
http://www.quaketerminus.com/quakebible/basics-move.htm Circle Strafing
One of the fundamental techniques you should learn is the circle strafe. Circle strafing is the skill of circling around your opponent while keeping him in your sights the entire time. The purpose of this maneuver is to be able to keep the sights on your opponent and shoot at him while dodging around in a circle. In order to execute the circle strafe, you must be strafing in one direction while turning your mouse in the opposite direction. The key to executing this maneuver successfully is to use smooth and continuous movements, especially when it comes to keeping your aim on the enemy. Although it's very unlikely that the enemy will stand still and allow you to circle around him, you can adapt your movements based on where he moves to keep him in your sights. A good way to practice your circle strafing technique is to find a pillar in one of the maps and circle strafe around it. Using a weapon that has a continuous rate of fire, such as the Super Nailgun, keep your aim on the pillar while circle strafing around it.
This is one of the things I dislike about FPS games because I think it's "unrealistic" that people would do this in real life, but you need to know it, one of the peculiarities of mouse/keyboard gaming.
As a general rule, I think ALL FPS online games have a certain number of people using hacks, exploits, aimbots etc. but remember, there's also a certain number of 15 year old boys who have unlimited time to play COD and get mad skills to where they can rule you. My basic assumption is usually that the person wtfpwning me is a legit player who's just better, and not cheating, but sometimes cheating is obvious.
Are you playing COD original or COD2? I'm just playing the single player COD2 now, but I have COD original also. If you like maybe we can make a server and practice techniques sometime. What username do you go by?
Games are different with respect to things like sniper aiming also. Most FPS games have awarded an "instant hit" to a sniper shot with someone in your sights, as if the shot arrived instantaneously, but Battlefield 2 is the first one I've seen where you have to lead the target based on distance. Not so sure about COD/COD2 yet but it seems like "instant hit".
PM me if you wanna practice circle strafe etc.
ON EDIT: FPS games that I have currently are BF2, Far Cry, FEAR, HL2/CS:S/DOD:S, COD2, and I have COD and Doom 3 but they are not loaded on my system at the moment.