Jax, the grandmaster at arms, is one of the funnest champions to play on Twisted Treeline, but, he is also a very powerful pick and can change the outcome of a game if played right.
Heres some reasons why and why not.
Pros

He can go matrix and dodge for 1.5 seconds.
He is op with a decent farm.
He can jungle effectively.
His burst is great early game if you follow my items and skill sequence (though of course change as nessecary for each game!)
He smacks people with lamps, I can't think of a better weapon in LoL.

Cons Yes, sadly he has these Q_Q.

He can get cc'd fairly easily, you can switch summoner spells for cleanse though if you want.
Hes been the target of nerfs for a little while (where the fu** did Irelia go?).
He looks like a purple fat ninja.
He sucks pretty bad early, luckly early game isn't very long in 3v3.
He is definently not the best jungler.
Umm I can't think of anymore.

Next!

For jax in 3v3 you want to pick either Q or E as your first skill, if your ganking and you get to the bush first, get E, if not, LEAP THE FU** OUT OF THERE BEFORE YOU GIVE THEM FIRST BLOOD AAHHHHHH!!!! Erm.. You then grab leap at 2 if you got E at 1, if you got leap first then get empower next, for level 3 get whatever skill you don't have. From now on level empower first, leap second, then E last (it dosn't get much better as you level it), and get ult at 6,11, and of course 16.

NEXT!

-Get Dorans sheild first so you can stay in lane as long as you want or boots if their that important to you early game.
-Pickaxe next, just try it, you won't regret it, I swear, It amazed me how much burst I got.
-Boots time if you didn't get it before, optional what you pick.
-Wriggles....wriggles is just so op... Not worth it too not get it on any ad melee champ, lets you farm faster and recover from 100000000000 damage from smacking minions a few times.
-Finish Hex Gunblade and you are pretty op now.
-Rageblade is self explaining.
-Ice Hamma! Slows, AD and makes you tanky, hardly you will ever get here but it's awesome if you do.
-GA, Guardian Angel, give you armor and MR, oh and the revive is pretty helpful too, oh and before I forget, unless you are extremely fed, if you have this item, people don't focus you.

NEXT!

Duh.
This is easy, take ignite and exhaust if you want lots of kills.
They can be switched out for ghost, flash or cleanse.

Early Game D:
I believe my title for early game is pretty explaining, IT SUCKS AS JAX... If you arn't using this guide! Pickaxe makes you OK early game. Just passively farm and try not to take too much damage and outlast your opponent.
-Random Tip: Moving around a lot is a tactic in this game, it helps you dodge skill shots and keeps you focused so you don't get shot by your enemy.
Mid Game :/
Mid's pretty fun as Jax, you have some core items and can easily 1v1 anyone, except maybe tryn and some other select few.
Late Game O_o
You let the game get this far, or their turtling like a bunch of bit**es.
Your powerful if you have all of your items, just kill the enemy when you can and push the turrets when you can.
-RANDOM TIP: If the other teams turtling, don't keep on killing their inhibs this helps them turtle.
Well then, I hope you won, if you didn't, you didn't try hard enough! GL.

NEXT!

I hope you enjoyed my guide, please don't get mad if this isn't how YOU build, this is how I build! Please don't troll, downvote without reading first, or have a fight in the comment section.

Please comment and rate my build. K thanks bye.