Thats my first build, but there always have to be one right? I was playing Vayne a lot already and decided to share my build and feelings about that great champ with you.

Here is one match of myself, showing Vayne.



Vayne have great harass at early game simply using Tumble everytime situation will let you.
After nerf, she is more of a carry than assassin, that's why she isn't so good at mid anymore.
Get a support or some hard CC champ and head bot lane.

Changes to vayne:
22.06.2011:
Silver Bolts will no longer interact with spell shields
Tumble bonus damage reduced to 40/45/50/55/60% from 55/60/65/70/75%
Condemn damage reduced to 45/80/115/150/185 from 50/90/130/170/210
Final Hour:

• Movement speed bonus now triples instead of quadruples
• Attack damage reduced to 25/40/55 from 35/55/75

That changes things a bit. They probably want make Vayne more of AD Carry than Assassin.
That is why i am not going for Trinity Force which is used in most Vayne builds around. With Trinity Force u depend on these hits every 2 seconds (Tumble Cooldown) too much, and its bloody expensive.

Pros:
Great Harass - Vayne is on of the best harassing champs in early game.

Range - You don't have to get close to enemy to make him eat grass!

Mobile - U can use Tumble to chase and to run. Also if you are in danger, use Condemn to push enemy back.
- Her passive gives you some extra speed when chasing enemies (+ulti triples that passive) so no one will run away from you anymore.

Great Damage - Her Tumble is like having Sheen from the very beginning.

Tank killer - Every tank stacking health gonna get heart attack when you will put 3 Silver Bolts on him.


CONS

Squishy - of course, damage and mobility have a price. She is squishy, so remember to get into team fights carefully, staying behind other champs. Also never face check bushes, you might not get out from them anymore.

Focused - You will find yourself chased by some champs for half of the map, just to make sure you will die. Tanks, assassins, they might come directly for you in team fights. Beware and be on your guard.

Items shown in purchase order are not "strictly follow". Many people using guides are building champs like shown - no matter who they face in game. Going for armor when laning vs ability power champs. Thats just an example. Use your head, that's just a guide! To help you understand Vayne better.
Doran's Blade:
It is good item to start. Gives little survivability, and some life steal, in case you run too low on hp. Just play safe for a while, and you will be like new born again.
Berserker's Greaves or Boots of Swiftness:
It's up to you to decide. I usually take Berserker's Greaves cuz it helps to last hit creeps and to hit someone 3 times to with Silver Bolts. If you really feel like you need more mobility, go for Boots of Swiftness.
B. F. Sword:
Try getting really soon, it helps a lot to last hit creeps, which makes you rich. Also it's a nice damage boost as for early game. Your opponents gonna feel that.
Infinity Edge:
Some attack, crit chance, and stronger criticals. That's what you need when you want to surprise your enemy. Critical now doing 250% dmg, with Vayne attack, that's a lot!
Phantom Dancer:
Here is the item, when i get my mobility back that i lost for buying Berserk's boots. It also gives nice crit chance boost and attack speed, so your infinity edge gonna be even more deadly.
Zeke's Harbinger:
Why i chose Zeke's Harbinger and not Bloodthirster? Because your damage output is awesome already, and it gives some attack speed. Also you need to stack Bloodthirster, and bonus is lost upon death, of course, if you own everyone, and you are sure you are not going to die, go ahead, take it, but Stark gives aura for team and reduces opponents armor which is useful for assassins, which have really low armor anyway. He wont know what hit him, and he already gonna lie on ground without breath.
Banshee's Veil:
Finally some survivability, it will help you when tank will try to catch you, stun you, slow you, or anything, you still got a chance to run away and prepare for a fight. Also some HP and magic resistance is useful. You shouldn't need that extra mana, but if you feel like you are spamming a lot of skills, that's gonna help.
Black Cleaver:
One again, attack speed for the win. Your Silver Bolts gonna make huge amount of damage. Also reducing armor and gives some damage, will help to take down anyone you will face in no time.

PS. Some of you might want take Madred's Bloodrazor in place of Black Cleaver. That might be good too.. just remember to take magic penetration in masteries then!

9x Greater Mark of Desolation Greater Mark of Desolation (Armor penetration)
Of course you need these, so your enemies gonna be afraid of every next bolt from you.
9x Greater Seal of KnowledgeGreater Seal of Knowledge (Mana regeneration per level)
These are very useful when you are harassing a lot. Though Vayne skills aren't that mana expensive, or when you are not fighting a lot, you can always spend extra mana to Tumble which will help you to Last Hit creeps. Some of you might want to replace them with some other seals, as mana regen is useful only in Early if you fight a lot. Greater Seal of Evasion or Greater Seal of Attack Speed might be good. Need to try them, might save your live, or help to last hit creeps.
9x Greater Glyph of Shielding (Magic resistance per level)
I am using these, because it gives me little more resist if i am going to lane against ability power champ, and in Late game might save you from being combo'ed in 0,5 seconds by some badass assassin.
3x Greater Quintessence of DesolationGreater Quintessence of Desolation (Armor penetration)
Same as first runes in the list, best defense is attack right?

In my opinion, choice here is pretty simple. In case you get surrounded, chased by some fast champs, or using Ghost you need some fast way to run to safe place, to take revenge later: Flash might help you to avoid certain death. Flash behind trees, avoid some heavy dmg skill, to escape from Crowd Control skill. You should know when to use it.
Exhaust Comes out very handy in case of someone diving you, when you are low on hp. When some1 is chasing you, or just simply to turn off some damage hitting you in teamfight, so you can take care of current target and then come back to that one.



Optional: Teleport will let you to change lanes pretty often, without long run, and putting yourself in danger of facechecking bushes on the way to other lane. It might also help you gank if you or your teammates have put some wards behind enemy line ^.-
Ghost is great to chase down retreating enemy, running away with low hp. It also might come handy when you decide to retreat, or to run from one lane to another, to make a surprise gank. With your passive and ultimate, its simply impossible for some one to escape from you, as long as he wont hide behind tower ;)


Its up to you, which spells fits your gamestyle..

Skill Sequence is pretty simple. Take Final Hour and Tumble whenever its possible. Why?
That question is pointless when it comes to ultimate, its just best that every champ might have, and Tumble gives you damage boost, some mobility, and every level of it is lowering cooldown. Silver Bolts are not that necessary in early game, as you wont OFTEN put 3 of them on the enemy. So bonus damage if you will is enough on level 1, but if you wont, nothing to worry, you will get enough attack speed soon enough.
Condemn so early might save your life in case of gank, or some heavy situation, or provide a easy kill if used properly.