Hey summoners!
This is my guide to the crit power Vayne (Highly recommended to try it out, before flaming!)
I tried this build in 10 games (I won the all).
Why I build like this?
Well, I think Vayne is really strong, but also really squishy. And afterall, she's an assasin, so she has to kill her target fast, and get the hell out of there, right? With this build, you will most highly 3 shot your targets, and be able to run away with the movement from both phantom dancer and trinity force + the rune. With this, you can come and go as you like, and will be able to kill a target REAL fast, without getting to much damaged.
The Banshee's veil is against stunners (Silver sash could be used aswell), because you wouldn't like to be stunned, when trying to kill the target fast, and be able to get away again. Vayne will not be any good in the middle of a teamfight, 'cause you would get focussed, and killed in a split second. My method is to flash through nearest wall, and Pop my ghost, to run behind them. When i'm close to them, I active my ultimate, and use my tumble, to roll over to them with stealth, which can be used to shoot the most dangerous of them away from you, and kill the squishy's in a split second, and let your team clean the rest.

Does this guide sound works for you? Please let me know, when you tried it out a few times. I would preciate feeedback ;)

- PredatorsCiSCii