Hey there. Thanks for checking out my 1st build. It's going to seem a little crazy, but trust me, I've had great success with it so far. I like very unconventional builds and this is one of them.
This build is all about Attack Speed with some crazy Ability power to boot. It's all about getting the maximum out of Fizz's W early on, dealing a SHED-LOAD of damage, then using his passive to slip away through the minions. So please, read it through and give some constructive feedback if you want. Thanks a lot guys :)

Here are my most recent matches. Definitely not the best, but I'm a very greedy player. OM NOM NOM
We lost the second match due to a disconnect from our tank. Shizz happens =/

Pros

Amazing passive that allows aggression early game
A lot of damage output mid-late game
Great at ganking
He's got a SHARK and looks like Stitch!

Cons

You need to farm well
No AoE for farming (only on Ultimate)
Mana early game is quite low
You will get focused if you play well (duh)
Oh and did I mention FARMING?

YOU NEED MID LANE!!

The items on this list are pretty expensive, and if you can't last hit, you're going to struggle. You need mid lane to maximize your early game harrassment 1-on-1. Laning with a buddy just doesn't quite cut it for this build :(

So, what's great about Fizz is his ability to close the gap between your enemy, and his passive, which ignores unit collition, so you can slip away easily. Max Seastone Trident 1st to deal a tone of damage, then Urchin Strike. Playful/Trickster is a great ability, but I find I don't need it early on.

You can start to harass quite effectively from lvl 2 onwards, so don't be afraid to jump on in there, especially with Exhaust.

Why Attack Speed?
If you build AP, you are very limited in team fights. You only have a small amount of mana, and waiting on cooldowns can be the difference between winning a team fight and losing one.
By building attack speed, you are getting the most out of you W spell, as well as allowing you to do a lot of damage when your abilities are on cooldown.

Q-W-AA-E-R.... Simple
Start with Q to dive in. Activate W straight away and start wailing on them with Auto-attacks. When they start to run, follow up with E to chase them down.
Finally, launch your ultimate to deal the killing blow if you haven't killed them by then.

PASSIVE. Almost like you have Ghost on constantly, without the speed boost. to top it off, minions deal less damage, again, encouraging offensive play. Who cares if the minion wave is on "his" side!?!? Kill him anyway.

Q Ability This is your gap closer. Learn it at level 2 for early harass and master it 2nd for damage.

W Ability This is your bread and butter. Learn at level 1 and max it 1st. This ability will deal a lot of damage with your attack speed and will make sure you get the kill if an enemy escapes.

E Ability This ability is awesome. It can dodge an enemies ultimate, hop you over into Dragon/Baron and late game deals a lot of damage. Learn at level 3 and max last.

R-ULTIMATE This is your ultimate, and it's animation alone is amazing, let alone the MASSIVE AoE damage, Range, and knock-up. 3 moves in 1! Brilliant for team fights and tagging that last remaining runner.

(I will add more detail to this later)

This build is about maximum damage, and with the reform to the masteries for Season 2, it opens up a lot of possibilities to be very aggressive. Stitch.. err, I mean Fizz is a champion which takes full advantage of Riot's direction for the game.
With this build, the style of gameplay is to dive in quickly, deal A LOT of damage, then get out of there.

I took Mark of insight for the AP items we will be getting, as Fizz's abilities scale with AP.
I took Seal of Alacrity for the added attack speed which is essential for this build.
Glyph of celerity for your ability cooldowns.
To round it all off, flat AP Quintessences Greater quint of potency for that added early game punch!

You may ask yourself, What about MANA REGEN!?
Early game, you can get a manna pot or two. Getting mana regen masteries really doesn't cut it, especially with the item choice below. Fiendish codex /Nashor's tooth adds even more mana regen during the mid-late game.

EDIT: I got rid of life steal in masteries as it added nothing beyond early game (Thanks Hokai). Instead, I maxed out mental force.

I take Exhaust because when you take the educated decision to dive in and grab a kill, the last thing you want them doing is getting away. I chose this because of the nerf to Flash.
A lot of summoners are still using flash, and exhaust combats it greatly.

I take ghost to chase an enemy down or to get away after diving into a battle.

I don't take Flash because of it's nerf. Plus you have abilities (Q + E) that can help you get away very easily. Don't forget your passive , which ignores unit collision.

You can take ignite . It works rather well, I just prefer to take Exhaust because your attack speed will do a load of damage, more so than a cheeky ignite. Plus, we are focusing on W, which will kill most people running away (unless they have a lot of HP regen). In any case, this is just my preference, take what you think is best. I've found I kill a lot more with Ghost & Exhaust than Ghost & Ignite.

(NOTE: You can swap in a Rylai's Crystal Scepter instead of using exhaust. Again, I like to get the lead early, so I can't wait 2/3rds into the match to build an item that slows for me.)

Fizz is new, so I haven't experimented with the other Summoner spells very much. Heal with it's massive buff may be one to check out, as well as Surge.

Attack speed & AP is king with items. I selected the items that work well with Fizz's W. Malady is an amazing early game item. It's a must for Fizz.

Why Malady?
Fizz is not a ranged AP character. He gets in close with AP skills and deals Melee damage with his Auto-attacks. With Seastone Tridant (W), he will deal more and more damage over time the lower that target's health gets. Malady decreases your opponents magic resist, so your AP abilities that you use after are super-effective.

For example:

You rush into a fight with Q, and immediately start attacking with W activated. The more auto-attacks you can get off, the less your opponents magic resist will be.
Therefore, when you activate E, it will deal LOADS of damage. Malady has an 8 second debuff time, so you have plenty of time to cast your ultimate and have it deal a lot more damage than normal. Couple this together with the Rod of Ages you have for added AP, mid-game you'll be pretty much unstoppable.


Fiendish codex is your friend for mana regen. Since adding it, and later upgrading it to Nashor's tooth, I've never had a problem with mana regen.

Lich Bane This is a MUST OWN item. Your next physical attack will deal an additional 100% of your Ability Power in damage. This will be your main source of damage dealing. With your attack speed increased, and you AP very high, it will rip people apart. It also improves your movement speed - (sure you have Ghost, but this is an added bonus)

The following items are your choice. Look at your opponents and see which best suits the current match.

Guardian Angel: I take this item because my build is all about the damage dealing. It doesn't give you a lot of survivability. By adding this into your build, you get some relief from the pesky AD carries and also an extra life to carry on killing! This has won many team fights - especially seeing how this build is about Fizz carrying HARDCORE.

Rabadons Deathcap: The AP ratio for this item with your ultimate is INSANE! If you have some meaty opponents to take down, and you're not all that bothered with a little more defence, grab this and watch the health bars drop.

Void Staff Grab this if your enemies have a lot of magic resist. Look at your enemy team. If they have a lot of CC, get Mercury treads instead of Sorcery boots and work a Void staff into your build for the added Magic Penetration :)

All out aggression.
If you're getting harassed by ranged champions in mid, dive them! That's what this build is for. You will deal tonnes of damage, and most likely win the fight. Then utilising Fizz's passive, slip through the enemy minions (which will deal very minor damage to you) and back to the safety of your tower.

I will add images to the guide. I just have a lot to do right now.
Try it for yourself and see what you get :) Thanks for reading.