the first thing i want to say is this build works. the 2nd time I used this build (4th time I'd used nocturne) i went 31-7-8 and at the end of the game could kill 4000 hp nautilus by myself while he had full health in between the time it took him to get from the front of his nexus to his healing platform. (sorry i don't know the name for the platform)
P.S. and for those of you who thought my last build wasn't informative enough check out this one

now when i was first considering making this build i was still thinking about buying nocturne, so i was looking at the lol store trying to decide whether i should get lee sin or nocturne, and i was looking at nocturne's abilities. The first thing I went to look at was his passive. and I noted 2 things his passive gave him life, and it did 120% damage to all surrounding enemies. What this meant was, the life he gained gave him resist in lane and he wouldn't need life steal until later than the other AD carries, (not that a bloodthirster or 2 wouldn't be helpful.) the 120% damage part had me thinking what if you got a critical hit on it that would mean that the critical hit would be 120% stronger which is alot more damage than a normal hit with his passive. and that is what this build is mostly built around critical hitting his passive to ramp up the damage. so knowing i could build a build off of nocturne I got him not lee sin. Now, the build starts of basic for critical hit items with the brawler's gloves. I found out first game, (remember the 2nd game i went 31-7-8,) which i played with the drafted beginning of the build that 2 health pots are helpful but in the beginning (and only the beginning) you need one mana pot because you use duskbringer alot in the beginning, (about every time it gets off CD you use it again, or at least you should be doing so.) and you can survive easy with one health pot because of your passive. now, once you reach 700 gold (if you can stay until 1100 gold and get a brawler's glove as well... great.) you should go back to get an avarice blade and boots, if you can only afford one, get the avarice blade. (always stay at the platform if you are 20 gold away from something with out avarice blade and 30-40 with it.) after that the next time you should go back is to get the zeal and vampiric scepter (it's fine if you just go back to get the zeal, but if you do that, you have to go back 450 gold later to get the scepter) of course, go back as soon as you can get the B.F. sword, and same with the bloodthirster, but after that you have a choice you can get the phantom dancer for speed or the berserker's greaves, which ever one you get first, you get the other one next. then an AD carry fav, the infinity edge, so helpful with continuing the idea of crit. hits especially with the crit. damage. youmuu's is for the armor pen, and who doesn't like damage with their critical hits. Originally I was going to make last whisper the last item just so the enemy would say "wait, what? but I just got a huge amount of armor?" but then I thought 'wait, what if someone like Amumu got thornmail' so I made it frozen mallet instead just to make so i was completely invincible.

exhaust and ghost are by far the best two summoner spells for nocturne. but i will allow a flash instead of ghost or an ignite instead of exhaust. if your playing dominion ghost garrison is probably the best but ignite will easily replace garrison. exhaust and ghost are by far the best in classic because in the complete beginning if you duskbringer someone as soon as they walk in the bush your in (before minions spawn) then you exhaust them while following them and killing them you can get rid of most of their life but once exhaust wears of even with duskbringer you'll need ghost to finish them off, but once you do this you'll be unstoppable for the rest off the game (as long as you don't do anything stupid.) of course that isn't all the spells will be helpful for. you can chase and run away with ghost slow down for the kill with exhaust. and because of how powerful Nocturne is, you won't even miss ignite.

duskbringer, i feel is the one skill nocturne needs. yes his ult, spell shield and fear are extremely helpful but duskbringer can speed you up if you need to get out of somewhere or chase someone. But that is not all duskbringer is for. it is a great ability to stand back and snipe with for a while before pursuing an enemy. like said in items you will use duskbringer in the beginning almost every time it gets off cooldown, and most of the times you use it will be to just snipe for some damage. duskbringer is also helpful for killing minions on hit and it'll help you get last hits if it isn't upgraded enough to kill.

now, it is your choice what skin you get, but i thought i would help you decide which one is the best.
normal nocturne: FREEEEEEEEEEE!!! and still probably one of his most BA skins.
void nocturne: rated higher than everything but frozen terror but still only 560, not as BA as it looks on the loading screen but still frickin' cool
frozen terror nocturne: this skin is the best skin because not only is it more BA than the normal skin but it is just just as cool as the void skin. it's only problem is it's the most expensive nocturne skin. at 920
ravager nocturne: worst of all skins and at the same cost as void. Really this skin should be called jack-o-lantern nocturne because it looks like nocturne filled with candlelight.

like any other AD carry, farming is essential, but it's so easy as nocturne i don't even worry about it, umbra blades late game can kill a huge group of minions, and early game can give you two minion kills per shot with it. (one you weakened the other the minions did.) I don't really know how to explain its easy, but it is, and as lame as that might sound, it's true.

Marks-Armor pen or straight AD: armor pen is more helpful in this situation because of the lack of last whisper, but there is nothing wrong with straight AD in this situation.
Seals-attack speed or armor: attack speed is the better one to get in this situation so you can wipe your enemies off the map but having a little defense is always helpful, and for when your getting red, its even more so.
Glyphs-critical damage or AD by the level: critical damage is better in this situation because most things in the build are critical chance, but it is always helpful to have more AD at level 18 then you would have if you got straight AD runes.
Quints-straight AD or speed: Straight AD is more helpful because if you do all of the ones that are more helpful you still haven't gotten any AD, but if you went with what i didn't say was most helpful you already have enough AD and you should get speed for running away and chasing.

both summoner spells are in summoner's wrath so there is no reason not to get it and AD is just basic for what to get in masteries. Attack speed isn't any less helpful then AD and the attack speed lets you get armor pen which (as stated in runes) is helpful because you don't have last whisper. the AD by level lets you get critical damage which is partially what the build is based around. the life steal is helpful because it gives you life which is already very low when you are an AD carry. and surely for the next thing i do not need to repeat myself on how armor pen. is helpful. the 21 skill in offense is great for Nocturne because it makes it easier to kill people right in the beginning, and it is easy to kill people in the end with it too because you have so much AD that it does more damage with the six percent. now after you finish offense you can either go with the extra defense, or runic affinity for red, i like defense more because you have so little until you get frozen mallet at the end, but there is nothing wrong with keeping red for a longer amount of time.

now my build is coming to an end but there are still a few things left to tell you not related to this build.
A) please comment and tell me what you think
B) clearly seen by the build's title I am not good at making good titles, so if while making a comment you could give me a better name for this build I'd be glad to use it.
C) the next build I'm going to make is either on Trundle or Akali so if you could tell me which one to do I'll tally up the votes and see who I should do it on. (you can vote on both in the same build)
D) also if you could include a name for the Trundle/Akali build with your vote I'd much appreciate it.