Hello,this is one of my many nocturne build before you read on I must warn you this build has a great weakness you have low armor meaning the AD carry can kill you in a few shots
only use this build if you are certain your team can keep the carry off your back while this build leaves you exposed to the carry it can very easily rape anything else for example an AP carry usually has around a 150 armor and 2.6k hp late game with ghostblade and cleaver + my runes you reduce the armor to 50 i have roughly around 400 AD so you will kill the AP carry in 6 or 7 hits the AS from W and ghost blade gets me to 1.900 so you need 3 sec to kill an AP carry it also lets you kill tanky dps with a few exceptions easily
though this build isn't good for 1v1 well it is good it is just not optimal

since i go jungle AS quints might be better for the jungle part
but since nocturne has very high AS and AD it is only logical to focus on armor pen
no need to explain the seals
for glyphs you can go anything doesn't matter i like per level mr so i can get over 150 mr when i finish my build

start with cloth or lifesteal scepter doesn't matter
always start with blue it is true that noc can jungle without blue
hell even amumu can but it speeds up his jungle a lot
start with Q after the golem is pulled don't use q immediately or you will have to walk out of it wait until the golem stops and then use it
after you are done with golem go wolves and waiths
then look around for a gank mid or bot ,top is rarely gankble [cause someone like lee or jarvan is there and they have too good escape abilities still check if you can]
if there is no gank chance [wasting there flash is usually worth it]
go golem and red then go b get boots ward and pots now you have a good shot of a gank cause people don't tend to have boots so early
as a jungler it is your job to make sure the other team doesn't take dragon so always get a ward for it
now for the items always rush wrigle directly after level 1 boots then get brutalizen and bf sword get phage and catalyst and finish cleaver and ghostblade after that get veil and and finish the mallet then finish get the bloodthirst
i won't talk about situational items because this build is very situational to begin with
never use it verus the 3 champs jarvan lee and poppy

you targets are the AP carry and the tanky dps [note the tanky dps and offtanks are different] though there are some carries you can deal with
ashe if she has used flash and you have ult is an easy target
corki after he uses Valkyrie
koggle is also an easy target
stay away from the other carries unless they have low hp
you can rape all AP carries easy [get qss for malz though]
there are 3 champions who are a big problem
3. jarvan his ult ****s you up and he is super tanky whilst dealing decent dmg his Q is dangerous cause it makes you even an easier target for the AD carry you can get flash to counter his ult but beware that his ult has a longer range than flash so just as easily his ult counters flash
2.lee sin is the master of kiting even though he has no range his damage surpasses yours he has two dashes he has armor shield spell vamp life steal in one spell he can slow your AS and MS you can't escape him if he can aim Q your ult is useless because of his ult
he won't be a problem in teamfights though at least not for you he will just go and rape your carry which will make your team use cc on him and not on the carry
also if he goes with irelia the game is 4v5 you will be missing a carry each team fight
unless your team is very good if irelia uses Q on the carry that's it the carry is dead lee will jump to irelia then kick the carry use Q to get to it and tempest ignite to kill it
your only chance versus him is to gank him a lot and have a very strong laner versus him jarvan or irelia are your best chances
1.poppy is the biggest problem you have if she has full hp and you gank her she will either live or kill you
her passive makes her an offtank with just a GA
but that's not the problem AD poppy is
AP poppy you can deal with once she blows her burst you will be fine since you will heal up
but AD poppy will kill 100% you can't outrun her your team can't help qss won't help [she will just cast her ult on someone else and mr won't help vs AD poppy]