As many people know, on COD 4 online people use martyrdom like crazy. If you pick up that grenade and let it explode in your hand, your death will count as a suicide and not a kill from the enemy. Works with thrown grenades as well. Happy Gaming.

Primary weapon:Barret 50 Cal.
Secondary weapon:Dragonauv:ACOG Scope

Perk 1:Claymore
Perk 2:Overkill
Perk 3:Iron Lungs

Having the M064E or something like that and get the R700 of course using the overkill perk (if available) and get the grip for the M064E and leave the R700 or the barret 50 cal. And leave them alone and then select your own third perk best place for this is backlot, wetwork or overgrown

For a powerful silenced weapon get the m4 carbine with silencer a desert eagle and make sure you get double tap and bandolier and you will have a good wetwork or bloc class

For a explosive class get the RPG perk and a shotgun, mixed with a M9 double tap does no good so get uav jammer and your own third perk

For a assault class get the AK-47 with red dot sight and your own perks UAV jammer is suggested

Hope I helped