Assault / Elite Assault:
While the rest of your team camps outside of the objective, plinking enemies off, you actually head into the objective and clear a path & making it safe for the rest of your passive team to run in for a quick and easy 10+ points.... then they complain about you being a noob who just runs & guns.
Elite Riflemen:
You don't like camping & don't like getting chewed up in close quarters combat like a rifleman.... and you don't like being made fun of for picking the Assault Class, so you pick this class instead.... You're still a Run & Gunner though, nobody's fooled.
Rifleman:
You think you're so special don't you? You pick the Rifleman because it's more challenging to use a rail gun to head shot a guy in a trench from 200+ metres away with one round and insta-kill someone with your magic bayonet no matter where you hit them.... you think all the other classes are too easy and are for noobs with no skill as you point & click people to death with ease of your uber accurate rail gun.
Engineer:
You like to focus on points for yourself. While you spam your SMG to drop tonnes of players, you're also nowhere near any of the objectives because you prefer to treasure hunt on your map for all the objects you can blow up. You run to one end of the map to blow one object up, then run to the other end of the map for the next.... then you run back to an ammo cache to reload, and repeat.... by the time you take out 4 objects, you're oblivious to the fact that your team is seconds away from losing.... or winning, either way it doesn't matter to you.
Anti-Tank Class: Two Types of Players
Type A - You're new to the game and think "Cool, I got this huge gun to blow up tanks!" and run off to a nice little spot on the map to wait for a tank to show up. If it ever does, you fire away at it over and over again, thinking you're doing something worthwhile, but you're over 200m away from it and doing nothing but allowing the tank to narrow down on your position and getting yourself killed. You then think you can use it to kill enemy soldiers, but keep missing because the Client Hit Detection is screwed up for the AT Rifle and only useful for targeting tanks..... oh wait, no it's not.
Type B - You've been around for a bit now and learned some harsh lessons. You drop your AT Rifle so you can run around faster and for longer because it's useless and instead, you run around with your pistol like a useless ticket killer waiting for an enemy's bullet to strike you in the head while you chase after speeding tanks with your AT Grenades.... you also take a page from the Engineer's book and wander off to look for destructible objects on your treasure map.
Machine Gunner:
You have a big gun with lots of bullets. You're a big man now. You like to run into buildings with guns blazing, trying to kill anything in there that moves.... if it's an enemy in another room, that's ok... you can just spam the wall until a few enemies drop. Other times, you will take a page from the Marksman's book and camp way outside of objectives or near team mates, but that's ok, because you still have a better chance of taking down more enemies than the Marksman because you can spam bullets in the general direction of the enemies and take out twice as many. When you are killed in your camping spot, you have a problem with learning from past mistakes and just plop yourself right back in the same spot, only to be killed again and again by the same guy who killed you the first and second and third time.... chances are, it's another camping MG or Marksman.
Marksman:
OoooOOooo.... Look at you, you were quick enough to snatch up this class before everybody else. Now you can run off away from the objectives and the rest of your team to look for some camping position where you can plink off one enemy soldier every 2 minutes, all the while thinking to yourself "Man I'm so cool".... when the round ends, you soon realize that you're at the bottom of the score board, just below the Engineer and AT Class guys.
Tank Crewmember:
The Tank Crewmember is an illusive species that even David Attenborough has trouble spotting. Every so often you can spot one in its natural habitat (The Battlefield) when they hear the mating call of a clan member or Steam buddy who already made a nest inside a tank. Unfortunately, this Species is more useless than your typical AI Tank Bot and usually ends up killing both inside their nest.
Tank Commander:
You don't care about leveling up or weapon progression, you just want to gain the most amount of points for yourself above the Engineer's own desires of points. You're afraid of bullets and dying a lot, so you stay inside the safety of your nest with only the threat of your three natural predators: Soldiers with Satchels, Commanders with Arty and other Tanks. If another tank crosses your path, the rest of the game vanishes and all you can focus on is that other tank for the remainder of the match.... like a dog and a car window.
Squad Leader: Two Types of Players
Type A - You're new to the game and see a class with a fancy gun. You run off like you're an Assault class, mowing everything down in your path while ignoring your spawning abilities for your team or that you can toss some smoke to help them.
Type B - You've been around a while and have been b*tched at too many times by team mates, so you take the extreme opposite set of tactics by staying outside of objectives and hiding in some hole for your team to spawn on.... you also pop that smoke to help your team, but you drop it right on top of your location, so the enemy knows you and the rest of your team that's spawning are right there, ready to be all mowed down the moment they take two steps forward.
Commander: Two Types of Players
Type A - You're new to the game and see a class with a fancy gun. You run off like you're an Assault class, mowing everything down in your path while ignoring your ability to force spawn players, use recon and drop arty.
Type B - You've been around a while and have been b*tched at too many times by team mates, so you take the extreme opposite set of tactics and hide way back away from any fighting and camp by a radio hoping for someone to mark arty for you while you just spam the recon button and force respawn... completely ignoring the fact that you still have that fancy gun, two smoke grenades, more capping ability than regular soldiers and there's many other radios on the map besides the one near your original spawn.
Did I miss any?