Scenario: You (BM) are caught by a rogue, and you either weren't standing on a freezing trap, or he resisted it. He cheap shots you. He has every advantage.
His fast attack speed means you are permanently poison slowed. Get your pet on him immediately. When cheap shot expires, cast intimidation. You have to wait until he is actually stunned, it has a delay. Watch his debuffs. As soon as he's stunned, (cannot reapply slow) you trinket, strafe, hunter's mark, enrage pet. You're at range now. He is going to spam vanish. You immediately flare, (or pre-flare). You're going to lose target, press your keybind for target last enemy. Pet attack. The whole time you're kiting, while watching your auto shot timer.
It all happens really fast and if you make a mistake you're dead. By the time he blinds and gets a kidney on you, he should be dead. This is where a rogue discovers that not all hunters are food. If he cheap shots and you're already standing on a freezing trap. You will humiliate him.
Scenario: You just witnessed a same level mage, and warrior gank someone. The mage is 30% mana, both are full health.
You open with viper sting on the mage, enrage pet, intimidate and kill the warrior (lupos should destroy him) keep viper on the mage and watch him try to run away when the warrior is dead. Those two classes, by the way, are your food.
Train resistances to cc on your pet. Especially frost.
Scenario: A hunter 5 levels higher than you attacks.
Send pet, intimidation... Get in melee range. If he hasn't used intimidation, Use one raptor strike/wing clip, and feign death. Hopefully he just scatter shot your pet. Don't get up until he has you targeted. Sit on his back and use your melee macro. If he's marks, he dies and you're 50% health. If he's BM, cross your fingers, but you'll probably still kill him; he just shit a brick in his pants because he wasn't expecting you to thump him over the head like that. A full 2/3 of hunters who have tested me, WILL backpedal in this scenario.
Scenario: Warlock ganks you. He has a blueberry.
He's got a full row of dots on you before you have him targeted, he sacs voidwalker, uses a health stone, and laughs over your corpse when you die and he still has 80% of his health pool. At higher levels, even if you gank him, he's probably going to kill you, even if you miraculously kill him first :D
Paladins, all you need to do is stay 20+ yards away and kite him to death. If you can't kill him it probably means you dont have lupos, or he's higher level, or has healing talents and you're going to end up with a stale mate. I've had paladins fight me for 5 minutes and then run away... if they're higher level, or annoying I often let them go at that point.
You'll probably end up melee'ing mages, especially frost, and other hunters. If you're ganking, stay out of ranged-range and let your pet fight for you first. If you're close enough to shoot, the enemy is close enough to charge in. (Druids/warriors) Only go in if he fights your pet. For druids, save your stun for when he pops out of bear to heal. Try to viper when he goes caster form. Scare beast when he's bear. Even if he comes out of bear to avoid the fear, you've still achieved something.
Priests can be complicated. It is very scenario dependent, but often you'll have to oom them to kill them. Don't be afraid to melee them just like if you were still playing your warrior. Stay behind him, and he can't cast on you.
Your melee weapons are NOT stat sticks while leveling. They're weapons that you need to know how to use. Keep the skill up. Get something that can proc damage, or a stun. (staff in ZF for example)
edit: Lol didn't realize I wrote a novel. My intention was to give you an idea of what pvp is for a hunter. My qualifications are an extensive career as a hunter in retail classic and TBC. Nowadays I never attack unless provoked, so my experience is mostly against higher level opponents and tag teams. My world pvp record is near perfection. 1 player in 20 has been able to best me levels 30-59. I have never lost against a same level opponent with the exception of warlocks, and one extraordinary rogue against whom, I've learned the lessons posted above.