Hello all! I'm making this guide because I see a lot of Vayne guides out there, and not many have optimal builds, so I thought 'Hey, I'll create an account, post my items, and see what people think.' So, here is my build, which I use in ranked often (when Vayne is not banned, which she is quite a lot to be honest). Please leave a comment and rating after reading!

Pros:
Great against Tanks, Off-Tanks, and Tanky DPS
Invisibility during ultimate is great for 1v1's
Ultimate is amazing, a free BF sword and a half every minute lets us focus on AS for Silver Bolts
A lot of fun to play, Tumble is a very different ability than anything other champions have
Pinning people to walls is satisfying :)

Cons:
Squishy
Easy to kill if she gets CCed outside of her invisibility
You might get a lot of flame for playing 'The new OP champ'

Night Hunter
A very nice passive that gives us easier harass early game, and better chasing throughout the game. The bonus is quadrupled when your ultimate is active.

Tumble
This is the ability that separates Vayne from other champions. Great for chasing, great for escaping, great for positioning during teamfights, great for juking out of bushes. When you get ganked, a great technique for juking is to run into the bushes, then just before they enter them, hit your ult and roll out, you can also flash if needed. This is a very effective technique and will save you often. You cannot tumble through walls, but you can tumble through the terrain created by Jarvan's ultimate. When pushing your lane, you can tumble before you shoot the turret, and you will deal extra damage. I don't know if this is a glitch or a bug, but for now, enjoy extra turret damage!

Silver Bolts
This ability is amazing for taking down those annoying tanky dps champs, while also good against other carries, supports, etc. This is the reason we prioritize AS over AD. Deals true damage, so it is very hard to stack armor against us.

Condemn
This ability is good for positioning as well. DO NOT fire this unless you are either getting a kill or knocking somebody into a wall. I can't tell you how many times I see champions with these types of abilities (Vayne, Alistar, Poppy) screw over their own teams by hitting somebody away or the wrong way. Try not to be that annoying Vayne that always ruins the gank :)

Final Hour
The ultimate. A free BF Sword and a half on a ridiculously low cooldown. Also gives you stealth every second and a half, along with insane chasing power due to increasing your passive. Use this often! Use it to escape ganks, to start ganks, during teamfights, to juke out of bushes, to attack turrets quickly. Most people are not aggressive enough in the use of Vayne's ultimate!

Health quints are very important for Vayne, the early level survivability when combined with Doran's Blade is amazing.

Greater Mark of DesolationArmor Pen Marks are standard for any DPS Carry

Attack Speed Seals and Glyphs might seem strange. I like to use these for better harassment early level, as well as procing silver bolts quicker. These runes suit my aggressive playstyle very well, but if you wanted to sub the glyphs for some MR, that is a viable option as well.

For Masteries I use a 22/0/8 build. This is great, as you get everything you want from offense, while still getting the added experience from Utility. I have seen some builds with 9 points in defense for Strength of Spirit. I use this on Ryze, but it is very poor for Vayne, as she has one of the smallest mana pools in the game.
My masteries change subtly from game to game, however. If I am playing ranked and I notice that they have a lot of physical dps (which they should not, but sometimes it happens), I will take exhaust. If not, I will usually run Flash/Ghost, in which case you just take the point out of Good hands in defense and add it into Haste.

I start with Doran's Blade, the early game survivability is amazing. I used to start with boots and 3 Health Pots, but the 100 extra health, AD, and life steal really helps too much to leave out. Next we take zerker greaves. I try to stay in lane until I have enough for these and a dagger, the attack speed is amazing early. You can exchange these for Merc treads late game if you are getting focused and CCed too much. After this we get sword of the divine. I cannot express how important this item is for Vayne. 60% Attack Speed is amazing, and we utilize both passives quite well. I usually try to map this item to the 'T' key, so in fights you can just hit R,T and you become much stronger. After you finish your DPS items, its time for some defense. These items are just as important as your damage items, if not more important!

A note: Do not get Black Cleaver. I know we are prioritizing attack speed, but Vayne really does not need any more armor pen than runes and Sword of the Divine give her. This, along with silver bolts, provide plenty of killing power for well-armored enemies.

Note #2: Do not get Sheen. I see SO MANY Vaynes get this item, and it really is **** for her. Yes you get ONE attack out of 3 with increased damage, but you are not Ezreal. Sheen's AP is useless, and the mana you gain isn't needed. It is better to go for more attack speed to proc silver bolts and Sword of the Divine passive. Do not, I repeat, DO NOT get sheen.

Again, self explanitory. Silver bolts is much more important than condemn. You will only use condemn once per fight, and you should only be using it when it will stun or for a quick hit when it will kill. This makes it MUCH less important than the true damage given by Silver Bolts.

Now that all the fluff and introductory stuff is over, its time to get into the meat of gameplay.

Laning Phase:
I always, always try to get mid with Vayne, she is one of the most competent harassers in the game. Her passive gives her a nice advantage when you are chasing them back to their turret. The standard harass is just like Phreak explains in the spotlight. Shoot, Tumble, Shoot, Shoot. This will proc silver bolts and tumble resets the attack timer, making this sequence even faster. At level 6 you'll get your ultimate, and become a real killing force. During laning you should be focusing on last hitting, not auto attacking creeps. You want to keep the lane closer to your tower than theirs, but you do not want your tower to take damage. This may seem very basic, but I cannot tell you how many times I see people auto attacking creeps, even at higher levels. When attacking turrets, be sure to tumble first, as you will get extra damage until the tumble cooldown resets

A note on your ultimate: Do not be afraid to use this aggressively. It is on such a low cooldown, you can use it often without any real consequences. If their jungler or a ganker runs out of the side bushes, turn on that ult and immediately tumble away into stealth. It will save you many times. If your lane opponent is past the middle of the lane on your side and commits a little too hard, use your ult. If you need to take down a turret, use your ult and tumble. Bottom line: Use your ult. Often.

Mid game:
This is when the ganks start, people start going around in packs. As mid lane, your job isnt to gank other lanes, it is to win and destroy mid turret. Try not to leave mid too much, as your lane is the most important. When and if you destroy their turret, then you can start to leave more, but always keep an eye on the creep flow of the lane, as you should still be watching to make sure that mid cannot get pushed too far towards your side.

Late game:
Teamfight phase. Never initiate, stay near the back, and focus the squishies. Do not wander alone. Standard DPS fight techniques. Use condemn on the person with the most aoe damage or team utility, then focus SOMEBODY ELSE. I know this seems strange, but if you pin somebody to a wall, or even push them away from the fight, they are incapacitated. By focusing somebody else, this gives their team 2 people that are out of the fight quickly. Trust me, it works. You should have your ultimate and Sword of the Divine active at this point, so roll around as much as you can to gain position and avoid getting focused.

My build is not set in stone, the only thing that I would say always get is Sword of the Divine. Depending on the enemy team comp, I will often switch it up.

Hexdrinker
This item is good if you are midding against a caster and you feel you need some extra MR, or if their team just happens to have a lot of AP. Particularly good if the enemy team has a Karthus. I will usually get this or Wriggles right after my Zerker Greaves if I need them.

Wriggle's Lantern
This is great if you are getting ganked a lot, if the enemy team is a lot of physical DPS, or if you just feel like you need some extra survivability in general. This item is very cheap, so if I need to get it, I will generally do so right after my zerker greaves. The ward is very, very helpful in low level matches because nobody will ever buy wards and the extra sight of dragon or baron can be game changing.

Madred's Bloodrazor
This item is alright if they are VERY tanky, but I find it to be a bit expensive for most champions that aren't Warwick. You already have Silver Bolts to take out tanks, prioritizing attack speed is more important than getting a Madred's. Yes I KNOW that it gives attack speed, but for the cost in gold, it is not as effective as other items.

Trinity Force
Alright, so I know that I said not to get sheen. And I still say sheen is a bad item for Vayne. I feel the same way about Trinity force as I do about Madred's. It is a great item, to be sure, but it isn't effective enough for its cost for vayne. Trinity force is amazing on hybrids like Poppy or even Corki to an extent, but with Vayne you just don't need the stats as spread out as this item gives them to you. To little of everything and not enough specialization for me.

Wit's End
This item is great, just like hexdrinker, against caster-heavy teams. I would get this against different team comps than I would get Hexdrinker, however. It is up to you to decide which of these you want, if any. Hexdrinker is better if the enemy team has only one mage, such as Karthus, whereas I would rather have Witt's End if they have 3 or more casters. It is up to you to decide.

Stark's Fervor
I will confess that I have never used this item with Vayne, so this particular section is very theoretical. I love Fervor as an item, but I don't think it is quite as effective as Sword of the Divine or Phantom Dancers. You could sub it for Phantoms if you must, but I love Phantom because it also gives you some much needed movement speed and crit change to go with your Infinity Edge

Quicksilver Sash
This is one of THE most underrated items in league. I will get this item in nearly every game that I am against a Malzahar. There are many uses for this item. If you want to get this is up to you, a good Malz is really the only case I can think of where I will 100% get this. You will have to look at the enemy team, assess who is doing well and whether you want this item.

Apparently, a lot of people only check out items and masteries, so if you've read my guide this far, then thank you! Be sure to leave a comment and a rating and let me know how this worked out for you, what you thought of the guide, and if there's anything I should add or trim down on!