I'll be up-front about this: I hate Free For All (FFA) games, especially Slayer, so I don't really have much to say about them. If there are some high ping FFA players out there that are having luck with certain tactics, feel free to email me and I'll put them here. I tend to prefer team games, as well as games with non-slaying objectives like Oddball, King of the Hill, Race and Capture the Flag, so I'll comment here on how dealing with lag affects those games and your role in them.
Capture the Flag
You've got a choice when playing CTF as a high ping bastard: do you want to play effectively, or do you want to go for the glory and risk being hated by your teammates?
There's no question that players with high pings are better suited to defending than attacking; especially if you have a vehicle such as a Ghost or Warthog, or even a Shade turret, to help you. (Teammates, of course, are even better.) Grenades are your friend while defending, if you can work out with your fellow defenders where you're going to throw so they don't rush in for a melee kill as you're lobbing one. (Work this out in advance of the battle, in the lull between attacks, not just as you throw one, unless you're using some sort of voice commo-- which for the high pingers, is pretty much ruled out as it eats up your bandwidth).
If you die (which you may) in most CTF games you'll spawn relatively close to your own base, giving you another shot at the flag carrier before he makes a clean getaway.
If you assume that high ping players are going to die more often (and in my experience, they do) it's better to have them defending; they know what's going on back at the base, and they know which way the attackers went, so they know how to respond when they respawn. If an attacker dies and respawns back at the base, he's not of any immediate use there unless he knows the situation, and more likely he's just going to be focused on getting back on the attack.
As a high latency player, if you're involved in a coordinated attack you run the risk of upsetting the plan by dying early, driving poorly, or creating unintended friendly fire, and thereby drawing attention to your high ping in a negative way.