Nocturne is one of the strongest Junglers this season, but aside from dominating the jungle, he is also viable up top, or perhaps even mid (if you're confident enough), where he is free to roam and make plays. I refer you to TSM's very own Ninjaken, who has been doing this exact thing with Nocturne in the games which he isn't jungling. This is my first guide so I'm not entirely sure how to code things, but hopefully this turns out ok :)

Pros

• Strong early game
• Pushes down turret fast
• Great at roaming and shutting down their jungler/mid laner
• Great at counter ganking if you take teleport instead of ignite

Cons

• Easy to overextend and very gankable
• Low scaling armor and health
• Easily harassed and zoned if forced to play a farming game
• Hard to CS with due to passive (but high early damage might help offset this)
• High mana cost

These are the runes I choose to use.

Greater Mark of Attack Damage For the extra early game damage for early aggression
Greater Seal of Armor Armour is definitely a necessity due to your early offensive built
Greater Glyph of Scaling Magic Resist You already have a spell shield, so you're not really in need of any magic resist early.
Greater Quintessence of Life Steal Who doesn't love extra sustain ;)

Greater Quintessence of Attack Damage This works as well if you can't afford lifesteal quints

This is pretty standard for me, and can be switched around if it suits you better. The way I based my skillpoint distribution on is on fast clearing of waves and ability to apply early aggression. Whether you max Unspeakable Horror over Shroud of Darkness first is your choice.

Duskbringer Gets the first point because it works well with Umbra Blades for fast wave clearing.

Shroud of Darkness This is maxed second with the first point at level 4 for the same reason, fast wave clears and split pushing. The Spell shield is also a nice addition :)

Unspeakable Horror The reason I put the first point in this at Level 2 is for the ability to mess with their jungler at their second buff once you hit Level 2. Alternatively, if their jungler is starting on the same side as you, you'd get Shroud of Darkness first.

Paranoia Gank, Counter-gank, Assassinate, Escape. What is there not to love about this Ult?
Did I mention escape? Yes. Escape. Caught in a 3v1? Jump to another opponent in range where you'd stand a better chance :)

Flash Is a must-get for nocturne. Using Paranoia to engage can get you trapped in sticky situations, especially during risky assassination plays. It is a necessity to help you disengage and also to help stick to people using Flash to try to escape your Unspeakable Horror

Ignite Is great for early aggression and helping you secure kills. It is however, possible to swap this for Teleport if you prefer to maintain laning pressure as well as having the option to counter-gank/roam bot-lane for a play. Ignite is also great for screwing with their jungler when they come to their buff camp for the first time on top lane and could possibly secure you a kill (possibly first blood). This generally works better if you start on blue side, as some junglers still prefer to start on blue rather than on bot side.

Teleport Like I mentioned earlier, is great for counterplay and maintaining lane pressure. I generally like to go with Teleport when I start on purple side, just because there's a higher chance their jungler would be starting on blue.

This is my usual start. Crystalline Flask is great for this strategy of reaching Level 2 as quickly as possible to apply early pressure on their jungler as it helps provide that extra mana required for your Duskbringer. It is also great for lane sustain.

Sight Ward is a great item to pick up as it helps you visualise when their jungler hits the second buff. Careful not to get caught out when warding the buff at Level 1.

An alternative start for a more passive start is Doran's Shield and Health Potion.

Rush Ravenous Hydra. It's great for top lane Nocturne as it helps you clear waves fast and still maintain a decent CS, while allowing for the choice to roam and gank other lanes.

Trinity Force is great if you're doing well, not so much if you're not. It offers great sticking potential and the 200% damage proc when does a lot of damage. However, it costs a ton and is huge burden if you're not doing so well. If you're in this situation, or find the need for other items due to the enemy's build and team composition, try going for Black Cleaver or Maw of Malmortius instead.

Boots really depend on you. You can build Boots first in the middle of your Ravenous Hydra rush, or you can start building your boots at the end of the item rush, depending on how you're feeling in the game. If you're finding roaming and ganking an extremely easy thing to do in your game, and on top of that, you're doing really well, get Mobility Boots for the fast engage potential. If you're having trouble in lane or prefer a more defensive build, build Mercury's Treads if they(Team or lane opponent) have a lot of AP or CC. On the other hand, if you're against an AD heavy team or your lane opponent is giving you trouble due to his high AD, get Ninja Tabi for the extra armour.

Enchantment: Homeguard and Enchantment: Furor are interchangeable I believe, if you find the need to recall and quickly get back into lane or into fight, Enchantment: Homeguard is the better pick. Other than that, Enchantment: Furor offers better sticking potential, especially when your Mobility Boots is off.

Randuin's Omen is generally gotten for its high base stats as well as for the active slow, which is great for an AOE CC during team fights, which is why I love to start my defensive items with this.
Guardian Angel is another favourite item of mine to build on Nocturne, mainly due to his tendency to get into sticky situations. This would also mean that you're likely to get shut down quite quickly. Guardian Angel allows you to buy yourself that extra time for you team mates to arrive and help you out if you do ever get caught out. This is however, not great if you aren't doing so well, as if you get caught out, you're most likely going to get camped down, hence wasting the item's passive.
Spirit Visage is generally a great MR item to get. Consider switching it for Sunfire Aegis when against a team with less AP. If your team doesn't already have one, you could opt to go for Locket of the Iron Solari as well. But this is usually unlikely due to the tendency for supports and junglers to build this item in Season 3.

These items have already been mentioned before and should be considered as substitutes for other items in the build, depending on both how you're doing and the opponent's team composition.

To be continued when exams are finished... :(

I NEED YOUR HELP!

For those of you who do try this build, please comment and let me know how well it works :) I want to know how well it works for other people other than myself. Even post a link to your recent games or a screenshot of the results.

Thanks in advance!