Brute Killing
If you want to kill a brute or anybody with a shield first you either want to take out the shield with plasma attacks or a shield drainer then just snipe them with something with a scope. Or just run up to him and punch him ( while avoiding his punches) and shoot him again or punch him again. Of course the easiest way is to stick him with a plasma or brute grenade and run away.
Grunt Killing
Grunts are quite easy to kill.You can easily take them out with a quick shot to the head or stick them (which is a good way to waste grenades).If a grunt pulls out two plasma grenades and starts charging at you then you have suicidal grunt!Dispose of it by shooting it in the head or sticking it.If it gets to close then you are dead.
Jackle Killing
There are two types of jackles:sniper jackles and shield jackles.Sniper jackles either have a carbine or a beam rifle.If it has a beam rifle if you are on heroic or legendary dispose of them quickly or they will do the same to you. Jackles with carbines will not kill you quickly but they will hurt get rid of them quickly with a well placed shot.Shield jackles are trickier. As you can tell bt their names they have a shield that covers most of their body. They have a little opening to shoot people out of if you shoot them there the will flinch upwards giving you the oppertunity to strike them with a shot or grenade.You can also use a charged plasma pistol shot to take out their shield then they are all yours.
Drone Killing
Drones re very easy to kill. They can inflict alot of damage to you though thats if you are not moving around. They will die to a shot in what appears to be their head. You can also spam assault rifle.
Vehicle Killing
Wraith
There are many ways to kill a wraith:First throw a shield degenerator or charged plasma pistol which both acts as a vehicle stopper.(it stops it for a short period of time and takes out all the shields of the people inside)Then if there are a guy in the turret then quickly shoot him in his shieldless head. Then if you are close quickly board it from the front or back. If you are far away then strife from side to side so the wraith shot cannot hit you then board it.
Scorpion
Scorpions are basically the same to wraiths except their missle shots go alot faster than a wraiths shot. The same strategy but if you are far away try to use a plasma pistol they go alot fast then the degenerator and still try to strife but be warned if you are not quick enough you will die if the driver is paying attention.
Ghosts
Ghost are fairly easy to dispoes of. You can still use the degenerator or plasma pistol to stop it then board it or just keep shooting the driver in the head until it is dead.
Warthog
For both types of warthogs( machine gun warthog and gauss or cannon warthog) are probably one of the hardest vehicles to kill. You can still do the degenerator or the plasma pistol but if it is fully loaded then you will have a problem. Turret or gauss the will both kill you in a matter of seconds. So if you do use the degenerator or pistol then the first person you should shoot out is the guy in the turret. Then there is only one more person who poses any threat the person in the side seat. With their shields out they should all be easy to kill with a well placed shot to the head. But you can always board either spot in a warthog.
Mongoose
These atv like vehicles are extremely easy to kill if you get killed by one I would laugh ever so hard.
Good luck on you travels!