Nocturne is one of my favorite champions to play in Dominion. In this guide I'll share my usual strategy for playing him, which has been very successful for me to this point. I've tried several builds myself and paid attention to what other Nocturnes are building around me in the odd game that I'm not playing him, and I've always felt most effective using this strategy as a baseline.

11/5/2011: I've changed my normal build to atmog's instead of Entropy/Sanguine Blade since they changed how much ambient gold you receive.

Pros/Cons are similar to how Nocturne plays in Normal games.

Pros:

• Mobility - you have good overall mobility, and an amazing ult
• Damage - your damage output is on par with or better than other AD carries, and, given the inflated gold structure of Dominion, you start to eclipse AP carries very quickly
• Fear - Unspeakable Horror is absolutely devastating in small team fights; at higher levels a 2 second fear is all you need to drop people
• Shield - Shroud of Darkness is also an extremely swingy ability. Shielding off a cc spell will save your life multiple times per game and get you kills you couldn't otherwise have gotten
• Ease of play - Honestly, one of the reasons I think Nocturne is so strong is because effective use of his abilities becomes instinctive very quickly; right click and faceroll item keys to win

Cons:

• Heavy CC - Some champs, like Ryze and Fiddlesticks, have devastating CC that require you to modify your build and change your general style of play; they're not unbeatable, but they certainly require tenacity (and Tenacity items don't hurt either)
• Thornmail - I've had games where my team wasn't very good in fights, but was at least able to defend three towers if I helped them win a skirmish to cap the third tower; this worked out fine until people wizened up and soon they all had thornmails to counter me

Exhaust This is best summoner spell in Dominion in my opinion: you drastically reduce a champion's damage output and keep them from escaping.
Ghost Your mobility is very good already, so you might not think Ghost is worth it, but there are plenty of opportunities to chase down a kill or sprint to capture a point in most Dominion games, and these can sometimes be pivotal moments in a game.

Garrison I like Garrison, using it correctly can save a turret or allow you to turret dive when you otherwise shouldn't be able to. However, I don't prefer Garrison over Exhaust/Ghost, as I feel that it is much more situational in its usefulness.
Promote I think Promote has value, but you already push lanes very well so it seems like overkill. I don't find myself needing the super creep very often, if ever, on Nocturne.
Ignite I'd only take this in draft if I was facing a very lifesteal heavy team, and most of the time I'd still rather have exhaust.

I typically use my Jungling runes in actual Dominion games, which means I actually use Greater Seal of Armor instead of Greater Seal of Evasion as I've suggested here. Greater Glyph of Scaling Magic Resist is also a carry-over from my Jungling runes. I like it, since I rarely have to build MR; you might try Greater Glyph of Attack Speed. Maximum armorpen Reds and Glyphs give you the most significant damage boost from these slots.

Out of the Gate:

Extra damage out of the gate, some mobility, and health potions to give you some early game sustainability. I use this opening set in 95% of my games as Nocturne.

Early items:
or
or

If facing a CC/AP heavy team:
Swap Berserker's Greaves for Mercury's Treads; start building your Wit's End

If you're behind early and can't afford Brutalizer, Avarice Blade can help you catch up in gold, and lucky crits never hurt. Also worth mentioning is picking up an early Vampiric Scepter if the enemy team is tank-heavy.

Mid game:
or

After your first team fight over Windmill, you should be getting a feeling for what the enemy team is capable of. Generally I've found that I either want to build Wit's End (against heavy AP teams) or Youmuu's Ghostblade (against everything else) first.

Youmuu's Ghostblade's Active is incredible, especially when your enemy is going to be feared. If you start with Wit's End, pick up Ghostblade next.

Late game:
With Ghostblade complete, tier 2 boots, and Prospector's Blade, your core should be done. Nocturne's damage output is pretty high with just these items, so I take this opportunity to start getting a bit tankier in most games. Giant's Belt into Warmog's Armor is usually my first priority, as you'll want to build up those stacks asap.

Standard late game build:


Against Heavy AP/CC:



Individual Item Discussion:
Kitae's Bloodrazor doesn't really seem necessary to me unless they're extremely tanky and don't dish out much damage themselves. Usually if they're that tanky they'll build Thornmails, in which case you'd probably rather have Lifesteal than a Bloodrazor.
Phantom Dancer has some great stats with some added mobility, if you're in a game that's going by very quickly and you won't finish atmog's early enough to get any use out of it, you might try PD out.
Entropy there's a ton of AD on this thing. The active is very good at dealing some extra damage to other tanky-dps.
Black Cleaver is worth considering if your team has a lot of heavy AD hitters and their team is tanky, but it doesn't give you any survivability, so I'd usually go with Sanguine Blade before this.