Nocturne is an extremely strong jungler both in solo Q and high level tourney play.
Nocturne can clear the jungle very quickly and with great sustainability. Nocturne also has nearly unavoidable ganks due to the fact that his ult lets you bypass wards by diving someone from afar.
This build for nocturne is the way I play him and suits my play style best, so feel free to change up the items or masteries.
Forgive the formatting I usually write these guides on my phone :)
Here is a little introduction to Nocturne video stonewall made as well.
http://clgaming.net/replay/2575/ here is a game with me playing Nocturne at high elo.
I use full armor pen reds/quints so I can stack flat pen with ghost blade.
I use Mr per level blues and flat armor yellows which are the standard runes for most junglers.
I listed the attack speed runes for quints, blues and yellows because having more attack speed runes will give you a faster jungler as well as stronger early game, but doing this will hurt you some mid/late if you gimp out the armor pen. So stick to 3 attack speed yellows 3 attack speed blues and maybe 1 attack speed quint. This is just personal preference.
You can do either 21/0/9 or 9/0/21 for Nocturne. I like 9/0/21 mainly due to util mastery, buff duration and increased movement speed.
There are two builds you can do on Nocturne but the core is the same on both builds.
The core is wriggles lvl 2 boots and ghost blade. The majority of the time you will get zerkers on Nocturne but in some extremely cc heavy games get Merc threads.
Build 1 is the one I have listed in the main build section. Wriggles>Zerkers>Ghost Blade>Banshee>Infinity>atmas> sell boots for Trinity
Build 2 is if your team needs a tanky initiate Wriggles>mercs>Ghost Blade> Warmogs>Atmas> Banshee/Force of Nature
I max Q first on Nocturne because it his main steroid+chasing skill. It also lets you clear the jungle faster.
Grab one point in w for the attack speed boost as well as the invaluable spell shield on active that it gives.
Grab E at lvl 4 and max it after Q so I can CC my target longer.
For summoner spells you can either go flash/smite or exaust/smite I perfer flash because you can flash over walls when counter jungling. Flash also lets you catch other people who flash.
Creeping / Jungling
There are three paths that I like to do for jungling nocturne.
The 1st path you grab a vamp scepter and do wolf>smite big wraith and clear>double golems Pill grab armor pots and do blue + full clear.
http://www.youtube.com/watch?v=oUWhQMPlB-c The route is shown in this video.
The 2nd path I grab a cloth armor +4 pots. Make sure it is 4 pots and not 5. You can even do it with 3 but I like to have 4 in case I run into trouble.
You start the jungling path by smiting the enemy blue wraith then running to your wolves>wraiths>Double golems
The 3rd path you start cloth armor 5 pots. Double Golems>Wraith>Wolf>Blue
Use your Smite on doubles and blue.
There are a ton of ways you can gank with Nocturne and that is why I love him.
The 1st way is you tell your team to push up bottom or top lane then sneak into the brush. Open with your q and e and be rdy to W any cc that will be thrown after you. You can use ult to catch the person once they flash because they will always flash.
The 2nd way is you ult in from behind your tower and open with Q/E and be rdy to W a spell thrown. This way is worse though because you will have to burn flash to catch the person if they flash. This is a good gank to use if everything is warded.
The 3rd way is pre 6 gank. You can just open with Q/E and hope to blow summoners. You usually wont kill someone with this. This is best done on middle lane. If you are blue side you can do this top lane as well by sneaking into the enemy jungle from middle and ganking top through their own jungle.
I like to play Nocturne to blow up squishies. Noc can blow up any AD carry almost instantly end game. You can try to pick people off who are farming alone but 9/10 you will get killed by the enemy team coming for you so make sure you know where the enemy team is if you do this.
In a team fight you can wait until the fight breaks out and ult onto any squishies to blow them up. One thing I like to do is bait their tanks into chasing me in a team fight, then I will ult onto their carry and melt him while the tanks have no idea what is going on due to darkness.
Nocturne can also do some minor split pushing. Have your team push mid while you take top or mid. If you are lvl 16 you can ult to mid from these lanes if you are in the right spot.