Hey, Welcome to my first guide and guide for Fizz. I will try to cover most of the gameplay of Fizz but if I miss something out post in the comments and I'll add it in and work on parts as time goes on.

This new little champion is insane, very very fun and possibly a little over powered at the time of writing. He can take some time to get used to but if you learn the in's and out's of his Playful / Trickster ability you can become a real terror.

Pros

Very powerful ability set
Nice mobility
Huge burst damage with Sheen/Lich Bane
Can poke/harass in lane very well with Urchin Strike & Playful / Trickster
Has a freaking shark friend!

Cons

Cooldowns are somewhat long
Not so great until he has his full skillset or atleast 3/4 of it
Fairly squishy
Requires good perception and reactions to dominate
Shark has no lazers

I take fairly standard Summoner Spells for Fizz in Ghost and Ignite.

Default Spells

Ghost: I take ghost over the peoples often favorite Flash simply because its much more reliable after the most recent Flash nerfs but the main reason is because of Playful / Trickster this ability really defines this champion and I will explain more about it in another section.

Ignite: I find Ignite to be a no-brainer with Fizz, his Seastone Trident combined with the new mastery Executioner make for some really deadly assassinations.

Other viable options

Surge Fizz can benefit massively from the attackspeed AND ability power with this spell making it a very powerful choice.
Flash Still viable without a doubt but I just don't find the distance worthwhile with this champion, I tend to use Playful / Trickster to get myself in and out of situations.

The runes I have listed above are just fairly standard runes, some alternate options would include flat AP quints and/or flat AP marks & seal. Flat AP is a viable choice for early game without a doubt but personally I prefer the magic pen, especially with the new mastery changes giving you 10% magic pen (down from 15%). I can't personally tell you exactly how to play your champion, if you want more armor/magic resist then use those seal types instead of the HP per level or flat AP runes.

Some people have asked why not use attackspeed but my answer is simple, your not an AD champion and your main focus isn't to stand and auto attack people. With this build you can dash in with Urchin Strike activate Seastone Trident poke and either get out or chase with Playful / Trickster.

(Passive) Nimble Fighter A very strong passive, reducing damage taken is always a good thing but to ignore all unit collision is amazing. It makes moving around easier and those pesky purple caster minions wont be so op with this.

(Q) Urchin Strike This will be your main gap closer & harassment tool, some things to note with this ability is that it will ALWAYS move the same distance regardless of your position, this can be a savior at times and others fairly annoying but overall interesting mechanic.

(W) Seastone Trident This is where your real damage will come from, just the passive from it alone is a large chunk of damage but activating also gives you a healing debuff and some additional on hit damage, try and make sure you get in atleast 1 melee swing during your harassment with Urchin Strike & Playful / Trickster to avoid any incoming damage & position yourself safely.

(E) Playful / Trickster Very fun and really defines the champion and what he is. A fun, tricky assassin. There is so much to be said about this ability - You can use it to chase, you can use it to run, you can use it to avoid damage, to slow your targets, and to even avoid turret damage.

One of my preferred ways to use this ability to Urchin Strike into a champion / turret range to harass with Seastone Trident activated, once you hit the champion you can use this to first avoid any return damage but also to negate the towers shot at you & the second active to move into a safe place. (Please note to perform actions like this your reactions need to be fairly high) You can stay ontop of your trident for a maximum of 0.75 seconds so reactions are everything.

(R) Chum the Waters Not much to say other than what an amazingly fun ultimate, this has a huge range and will only attach to a champion. It's a very useful ultimate and can be used to escape, initiate team fights or even disburse team fights and pull them into your favor. Its pretty straight forward and really is the icing on the cake for this champions repertoire of abilities.

My item sequence is pretty general as these items are just a great selection all around for Fizz.

Early game

Start with Doran's Ring and on your first return back pick up Boots and Sapphire Crystal (Or Catalyst the Protector if you have enough gold.) If you don't want to pick up a Catalyst the Protector first take Sheen then Catalyst the Protector but either way you want these two items as early as possible. Also don't forget those Sorcerer's Shoes!

Mid Game

Turn your Catalyst the Protector into a Rod of Ages the earlier the better with this item. It will provide you with a ton of additional survivability, ap & just top off your mana. Once you have Sheen and Rod of Ages start building your AP with Blasting Wand/ Needlessly Large Rod and turn those into a Rabadon's Deathcap asap.

Late Game

For your final set of items you want to turn your Sheen into a Lich Bane, you will see a dramatic increase in your burst damage once you have this item. If you find yourself having trouble staying alive think about pursuing Rylai's Crystal Scepter before your Lich Bane. The Sheen proc alone will still be a nice chunk of additional damage.

Final item

The final item is always situation depending on how the game is going. Getting focused down too easily? Think about building a Zhonya's Hourglass it will provide you with those valuable 2 seconds for what ever reason be it waiting for cooldowns or avoiding big nukes/focus fire. If you find yourself having a storming game and no real danger of being killed you can move to the Malady a very strong item on Fizz in all areas. Also if you find yourself having a hard time surviving long enough to take down those atmogs champions Deathfire Grasp will make them rethink there decisions.

Quick Summary

Fizz is a very versatile champion with many item path options and game play styles available to him. Once you master him I believe you will love him forever and even stop teemo from getting more skins!

All I can say now is thank you for looking at this guide and getting this far. This is my first guide and I will try to update it regularly, include additional builds & item choices and will take some recommendations from others to. I apologize if I have missed something out, if you find something make a comment and I will get onto it and fix/add it asap.