Nocturne is a great champion because you can build him in lots of different ways. My opinion is that Nocturne is one of the best carry's in the game because he can do 1v1 on almost any champion when at level 18. He can hold his own against 2 enemies in the lane and can outlast most champions with clever use of his passive.

Nocturne can be built as a pure dps nutter to 2 shot people at lvl 18 with no armour. And it is almost impossible to run away from him.

Pros:
-Great at 1v1 and 2v1.
-Can 3v1 or 4v1 if enemies dont have cc's.
-Ultimate is one of the most OP in the game when used well.
-One of best laners in the game because he can 1 shot entire mobs with his passive.
-Better when lots of enemies around because passive heals you lots.
-His got a 2 second fear that does 250 dmg before hand.
-Blocks one spell effect then gives you a big attack speed boost. (Great for mages with roots)
-Ulimate can be used to run away or engage. (Great for engaging team battles half way in so you don't get focused)

Cons:
-CC'ed very easily when unaware.
-Doesn't have much health and can get focused easily.
-Like any other carry but a bit more survivablility.

I go for Attack Damage and Critical Strike Damage runes because you will be criting most of your hits and they will be hitting for 1.5k on minnions and about 1.2k on other champs with no armour.

I go for Attack Damage moves and Armour Pen mostly in Offense Tree then the rest into Utility Tree for faster respawn time and more xp to get to level 18 the fastest.

I go for Dusk Bringer first because it gives you a great harassing move that increases your attack damage by a very nice amount aswell. The other 2 abilities i generally go for Shroud of Darkness first if a mage heavy team then level Unspeakable Horror but other way around if very melee heavy.

Dorans Blade should be first to be bought because it has attack damage, lifesteal and health.

Beserker's Greaves are next to be bought for increase attack speed and movement speed.

Infinity Edge is what makes Nocturne a great carry it gives you increase attack damage, crit chance and your crits hit a lot harder.

The Bloodthirsteris your next item beacuse its got attack damage and life steal. It has a passive that increases its bonuses by 1 per kill up to 40 attack damage and 10% lifesteal, at full stacks you have 100 attack damage and 25% lifesteal. You can 1v1 almost any other champ at this stage.

Phantom Dancer x2 is your next items because this will cap your attack speed and give a massive crit chance which is what you need most by now. You will have lots of movement speed to catch any champion even when they pop ghost just use Duskbringer.

By now you are pretty much unbeatable and can kill people in less than 1 second.

For more overkill by The Black Clever if they are getting some armour but if they are not then go grab another The Bloodthirster, just make sure you have both at full stacks and you are now the most OP champion in the game.

Nocturne scales very will with attack damage, crit and attack speed. Attack damage is the best move for nocturne because his ultimate, Duskbringer and Shroud of Darkness all get a benefit from it. Crit is second most important due to most of your damage comes from your massive crits, and at level 18 with 2.54 attack speed and almost 100% crit chance you will 2 shot most characters in less then 1 second.

His Ultimate is great for engaging team battles, if you stay back in a bush way out of site from the enemy then Ultimate in when the battle is engaged you will be a lot less likely to get focused.

Duskbringer should always be placed when fighting a battle, it gives a massive attack damage bonus and on hit it does damage to the enemy and they drop a puddle you can get incresed movement speed from.

Shroud of Darkness should be used mainly when going against mages because you block one of their spells, try block a root or cc with it and once that happens it is gg for any mage when your full decked out.

Unspeakable Horror is really good it does 250 magic damage and if they don't get out of range which is literally impossible when you hit them with Duskbringer unless they have flash.

Nocturnes passive is so beast because it gets better when you are fighting near enemy mobs because you heal yourself by about 50% when you hit the whole mob.

At full gear just watch how fast people drop and if u see anyone that is by themselves you will be able to kill them pretty much doesn't matter who they are.

Always sit in a bush and pop out from behind when against range champs to definatly get a kill, just make sure when its a mage pop Shroud and watch him QQ.

Just remember play it smart you should be sweet to 1v1 anyone and sometimes 2v1 if their are no cc or slows. Smart use of abilitys and timing is key to major success in games.