Fizz - The Tidal Trickster is in my opinion one of the best mid's in the game. He is so powerful and this guide should help you on your way to dominating mid lane. His burst damage and un-targetable flip allows him to dominate most mid's.
Activating your W before using a Q in at level 3 allows you to do a lot of damage. If your lane opponent tries to damage you with spells than hop away with your E if not then use your E for even more damage because the lower their health is, the more damage the bleed does.
Pro's and Cons
Fizz has a tonne of burst damage with high mobility.
He brings a lot of crowd control into a team with 2 AoE slows.
Easy to shut down after he has used his E.
Building Magic Resist makes him suffer more than others.
Overall I think Fizz is a great buy and pick. Early on you can get kills with ignite+bleed combo. He can shut down squishies in seconds and he has lots of mobility. He also counters hard anti-carries like LeBlanc.