I'll get this down now, I tend to use the scavenger perk and carry a Stinger Launcher - very helpful in taking out enemy harriers and choppers but for team based stuff, the sweetness of it is taking out UAV's. So I will volunteer to be Anti-Air man, if you like.
On small (ish) maps like Favela, or Rundown, I think one good tactic would be to have 3 teams of 2-3 players. Split up at the start, and don't follow each other arse to arse, keep some distance and spread between you. Team 1 goes to the left flank, Team 2 the right flank, and team 3 stays as much central in the map as possible.
Team three has the job of actively engaging the enemy, so if it moves - shoot it, even if you miss. Because Hopefully this way, this will draw the fire and/or attention of the enemy players who aren't trying to flank themselves. Giving our flanking teams oppertunities to get to the rear of the opposing team.
While this is going on, the flanking teams should either have silencers on or if you don't have them, try to slip past the enemy if you can (even if you see them), unless you can knife kill the bastard(s). Use buildings and good eyes-on positions, but dont stay there too long. The overall point is to get to the enemy side of the map, regroup with the other flanking team and form a sort of line, or as much of one as you can, across the map and push back in the direction you came with full lethal force, and fuck the enemy's shit up from behind. (and again, space and spread between you)
The supressing team (Team 3) should be taking most of the flak, a couple of deaths involved maybe. But I find a lot of it is about attention grabbing. People seem to rush for the closest red dot - and thats a beutiful thing if you have guys trying to flank.
So providing that all goes well, the flanking teams (however intact) should make it back to the original spawn point, swap the teams around or not, and repeat this process.
You may find that we can only end up "finishing" this whole process only once in an entire game (Depending on the pace), or we could end up repeating it several times.
So,
Basically team three - rush forward, cause a fuss, keeping enemy players on thier toes. (Maybe plant some claymores about)
Teams one and two - Go right and left, engage if necessary, regroup at other end of map. Both teams disperse in a line, and push back with full force until you get back to our spawn point.
A bit long-winded maybe, but it's a tactic I've always thought would work on COD, due to people mainly expecting to be safe from behind, and also the fanatic rush most players have to the nearest or last sighted red dot.
And to my bro,: I'm really trying not to sound like I know it best beacuse I'm in the army, honest. Do tell if you think that it's a croc of shit.
Edit: here's a map I just threw together, again, maybe a bit longwinded but a picture paints a thousand words, as they say. As you can see it's pretty much a big loop:
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