Fizz is a verry great assasin champion, that rely on his big AP scales to do great burst dmg and then effectively escape from fight, or to chase. So why play him as AD?
Also this build is a little modification of Siv HD's build. So if you want to try this, i recommend you to look at his youtube channel.

If you never played Fizz, and you are looking for good guide, please, this in not for you. Go rather look at someone elses guide.

This build focus on damage converted from health with Atmas.


(Sorry for my english :) )

Maybe you are asking you self - "WTF AD Fizz?, it is wasting of his abilities". Well, I will be honest, it is. So lets go look, why I decided to play him as AD.

From lvl 3 with boots and potions, you are little bit weaker than AP fizz, but you can sustain more damage, thanks to runes. But after you buy first doran blade, things will change. +10 damage + 100 health and 3% life steal will change your early game into killing spree paradise. But be careful with your mana, this is reason, why you should buy one mana potion at start.
You will do pretty nice amount of damage with autoattacks, but your W is adding % damage of enemy missing health + dot + bonus damage. Combine your W with Q and you will get so much burst, it is insane. After getting seccond doran blade and sheen, enemy should be scarred as hell, when they will see you comming. Keep using your E just for dodging their CC or to escape from turret, if you tower dive - E is NOT your damage ability as AD Fizz, so use it wisely and dont waste it, if you can jump on someone with Q, dont use E.
Really, get to Trinity force should be no problem, problems will show up, mid to late game, when you are stuck only with Trinity force and you need to build Warmogs so you can start using Atmas after it. This phase can be pain in ***, but when you get over it, it will be hell for enemies. You will get little less damage than AP fizz in that part of game, but 2-3x more survival ability. Your Q is still damaging as hell, and you are not affraid to rush into 3 enemies alone to get kill and then escape.
Late game you should had no problems to move through battleground, enemies will probably not focus you, because you will have about 4300 - 5400 hp (5400 if you have all items) + really much magic resist and armor. Basicaly, you are tank with great damage, enemies are affraid of you and only way how to kill you is screw something up, or let them gank you 5v1.
You will have about 300 attack damage (that is not so much, but still it will provide you enermous damage with Q + W + Trinity force).

And this is it.
AP Fizz got more damage, but really cant be long in team fights.
AD Fizz got less damage, but he is not the one, who is escaping from team fights.. enemies are.

PROS:

- Verry tanky
- Better early game harass than AP Fizz
- Great chaser
- Great escape abilities
- Great ganker
- AD fizz is much underrestimated
- Sheen, red buff, his W, slow from Trinity force and autoattack proc on his Q + some bonus damage from Q it self.

CONS:

- Not so great damage late game as AP Fizz
- Expensive items
- Item dependent
- You will get much flames from teammates (if you dont play premade with people you know), it is even worse, when you actualy failed that game at some point.

What to take:

Flash
Ghost
Exhaust

Seccondary option:

Ignite
Teleport
Surge
Heal (in some cases)

RED: Armor penetration - as a AD champ, this is a must
YELLOW: Armor flat - good if you want to solo, to sustain more incomming damage
BLUE: Magic resist flat - same as armor, but against magic damage
QUINT: Movement speed - great for chasing/escaping

I think there is not much to explain.
Simply: You need armor penetration, because you are going AD, but fizz is basicaly mage, so you will need definitely magic penetration too => full offense masteries.
I have utility for more mana, movement speed, and improve flash.

Boots
Dorans blade 2x
Sheen

This is yours early game core, you must have. This will give you really great early game burst.

Ionian Boots of Lucidity
Phage
Trinity force
Giants belt
Warmog's armor

This is yours mid game build. This is, where you get stuck for a longer duration with damage, until you get through Warmogs to Atmas. But then it will be just better. If you can get through this phase, you shouldn't have any more problems in game.

Atmas impaler
Banshee's veil
Warmog's armor

After you get Atmas, your damage will rapidly increase, this is the point, where things will get interresting. I usualy pick Banshee and seccond Warmog after. This will secure you 5 400 healths at full stacks and you will be nice tanky with little less damage as AP fizz.

Well, I hope you like it. This was my first guide for people.
This guide was meant to show up, that AD Fizz is viable and worth to play, but if you really want to play Fizz as it should be played, this is not for you.
I find playing champions in other ways interresting, and this really works.

Sometimes is solo top pain in ***, because Garen can spin to win you out of lane pretty easy, or Yorick will send his minion army on you, and the only thing you can do is stand under turret. But there is always something you can do nothing about it, even if you play properly or not.