Hi this is my first guide generally so dont be very strict.This guide is about Jax (Dah).Jax is one of the best champions i have ever played mostly against squishy targets like Sona or even Fiddlesticks and against DPS targets like Trynd or Xin Zao.

Pros
-Can make your enemies DPS targets think that they can kill you but they get owned
-Can make great escapes with the LEAP STRIKE.Trust me when the enemy sees you fleeing while jumping on a friendly minion especialy when u are exchusted makes the enemy rage soo much.
-Can dodge and make your enemies troll in fear.
-Can farm quite well with the RELENTLES ***ULT
-99% You will win a 1 v 1
Cons

-Makes you think you are invincible especialy with dodge chance 32% but you are not
-Never go in gank first you cannot beat them.AND NEVER THINK HE IS A TANK!
-If you play aggresive you may end up feeding.You need to play carefull and strike where your enemies are weak.

For items when you play Jax you want to play AP with attack speed so you can auto-cast your ulti and deal more damage.Your items that are must are the guinsos rageblade and the Relys Scepter.Why?Because with your ulti you can make your attack speed go 2.00 without any items but only rageblade.Relys crystall scepter is for when you cast your Leap Strike and making sure the target does not run away.

For masteries i go 24-6-0 because when jax you want to make sure no one escapes u when u 1 vs 1 or even fighting more enemies.I go with offencive masteries to avoid that.I hate how much many champions manage to survive my onsault and leave with a 150 helth.So yea offencive items for the win.