A.
Rushers This is my favorite style.
Rushers are always on the move looking for enemies to kill.
If you practice and get good you can get a lot of kills.
Odds are in your favor.
Also make note that this is likely to give you a lot of deaths too.
B.
Snipers A good sniper is a huge advantage on any team.
When you start out, you will more than likely only be able to kill campers and other snipers, its a lot easier to kill a sitting target and it takes a good bit of practice to before you will be able to hit moving targets.
On top of that, Also normally your enemies don't die with 1 kill unless your playing hardcore games or a headshot.
C.
Melee attackers I would consider Melee attacking to be type of hybrid playing style.
You will see some people are pros at it and could take out a whole team.
They're very fast, cant detect them, silent.
Aim for their feet and Beware of the ninja.
D.
Campers I don't think anybody likes campers not even other campers.
Why? Campers try and find a high traffic area and stay there.
They try and make kills as easy as possible.
They are a real pain in the team games.
Make sure to give every style a good chance, to find the best style that fits best and works for you.
Except if it's camping.
If you do, please just don't play.
Ever.