This build allows you to kill just about anybody, at any point in the game in a very short time.

I play him as an assassin usually roaming mid, near a speed boost assisting where fights break out. If I'm playing vs any invisible I always have Oracles. It really ends Shako's, Eve's, and Akali's game.

Pros:
Does ridiculous damage
Life steal keeps you alive
People fear you
Good surviveability for the damage heavy build
Can close the distance easily

Cons:
Vulnerable vs magic/stun/dodge

With this build you have low health and are an easy target, but you deal ridiculous damage. To make up for this, always get the jump. You must initiate the fights at the right place and time. You will be most successful if you stay out of sight until the enemy initiates the fight on one of your teammates. As soon as they commit to the bait, dash in, your dash will make their corn pucker, and it'll slow the enemy, and knock them up in the air. By the time they change targets it's too late.

Focus on invis, assassins, and ranged chrs, you can usually kill them in one burst of charge/tallon strike.

Watch out for:
Jax - his dodge and stun will beat Xin if you fight alone.
Rammus with thorn mail - You do so much damage, and have so little life the thorn mail will end you before you can end him, avoid this fight if you can.
Teemo - You have to play this one right, let him blind you, run, charge only when blind is expired.
Sion - The combination of his stun, shield and ult will usually beat Xin.

Challenge - Passive - Gives you some health every 3 attacks. Stacks well with attack speed

Three Talon Strike - Next three normal attacks do bonus damage, and the 3rd strike knocks the enemy in the air. Get only one point in this skill in the beginning for the knock up ability, leveling it does not give you the same kind of benefit you get from Battle Cry or Audacious Charge.

Battle Cry - Passive - increases attack speed - Active - for 5 seconds each hit reduces the cool down of all other abilities by one second. Stacks well with attack speed.

Audacious Charge - Damage, AOE slow, and closes the distance - this skill is what makes Xin dangerous.

Crescent Sweep - Ultimate - does great AOE damage.

When attacking, initiate q and w then charge with e. after the dash use your ult, it's % health based so it'll do a lot of damage. Your 3 talon strike will knock them up and by the time they hit the ground they will be on the run or dead.

Exhaust- excellent for a 1vs 1 kill, good for escape in a pinch
Flash - good for escape, and for getting in range for a dash
Ghost - Good for any dominion player
Promote- Good for lane pushing
Garrison- Good for any dominion player

It's a lot easier to capture points with everybody is dead. Play Xin well that dominion is easy. This build does 1000+ damage a second, and combination of crits and life steal will keep you alive.

Whenever Jarvan III, the king of Demacia, delivers one of his rallying speeches from the glinting marble balcony atop the Royal Palace, Xin Zhao is at his side. Coined the Seneschal of Demacia, Xin Zhao is the personal steward of the Lightshield Dynasty. His enigmatic, silent vigil has led to an abundance of conjecture concerning his “secret life” and origins. Whether it’s "Zaun double-agent" tendered at the dinner table or "indebted rune mage" mused in the editorials of the Demacian Constant, Xin Zhao betrays no hints to sate the curiosity of the masses…for good reason.
Prior to the formation of the League, Noxus was renowned for a spectacle called The Fleshing. It was a gladiatorial event with a cruel twist: as a fighter won matches, his number of opponents (generally prisoners of war) fought simultaneously would increase. This meant eventual death for every contender, but with unparalleled glory. Xin Zhao, known then as Viscero, was slated to face 300 soldiers, nearly six times the previous record. This was clearly meant to be his final match. Jarvan II, hearing of this unprecedented feat, infiltrated the arena to offer him an alternative: serve Demacia and punish those who ultimately sentenced him to death in exchange for his freedom. Xin Zhao accepted, astonished that a king would risk his own life on his behalf. Under the cover of a prearranged Demacian assault on Noxus, Jarvan liberated Xin Zhao and his 300 opponents. During their retreat, Xin Zhao took a poisoned dart meant for Jarvan. This act of loyalty, from a man who vowed no allegiance, earned Xin Zhao a spot at his side until the day the king died. Now in the service of his son, Jarvan III, Xin Zhao is stepping into a new ring – the Fields of Justice – to fight for his adopted country and to honor the legacy of the man who gave purpose to his life.

"Death is inevitable; one can only avoid defeat."
Demacian Manual of Arms

Upon selection
"To the arena!"
Movement/attacking
"A Demacian does not retreat."
"Always forward."
"Here's a tip, and a spear behind it!"
"It shall be done!"
"My king commands."
"Only actions truly speak."
"Perish with honor."
"Press the assault!"
"Sound the march!"
"Their lives are forfeit."
"The warrior's spirit is never broken."
"To triumph!"
"Victory calls."
"Fate has made its choice."
Taunt
"I may be outnumbered, but not even the odds can stand against me!"
Joke
"Find me an immovable object, and I'll put this question to rest!"