Here are some ideas I think would make cool perks;

???? : You do not drop your weapon when you are killed

Theft : When you kill an enemy, any ammo remaining in his gun is deducted from him ammo count when he respawns

Helping Hand : when you kill an enemy, half his killstreak progress goes towards your killstreak progress

Conflict : Enemy makes a distinct sound when in your area

Decoy : When you die, you lie down as if you were going to last stand and fall straight to the ground, buying you a few extra seconds since the enemy will believe you are in last stand

Ricochet : Any projectiles fired at you are deflected, also a small chance that enemies bullets will ricochet giving them the potential to kill

Bloodhound : Areas where team mates and enemies have recently died are pinpointed on the map for a brief amount of time


These are all I have for now, kinda lame I know but im trying to think of more.