Ahhh, Jax. He's the ultimate champion. He has good defense, epic dodge, and deals out massive damage to anyone he encounters. If you use this build, you will have absolutely no problem taking out any champion within the League. Now, this build can be modified in game depending on how you see it. If you're facing a high HP/armor tank, you might want to substitute a Hextech Gunblade for a Madred's Bloodrazor or Last Whisper, as you see fit. Anyway, I hope you find this build helpful in increasing your rapage upon the League of Legends.

Greater Mark of Insight - Magic Pen is a must, as Jax's hardest hitting skills deal magic damage. You don't want any of that blocked, now do you?

Greater Seal of Evasion - Jax's dodge rate is the key to his success, the more you can dodge, the more you can activate Counter Strike and stun everyone around you. It's outrageously effective in combat, along with being useful for escapes, as you have a higher chance of dodging attacks that come your way.

Greater Glyph of Focus - Every champion can benefit from increased cooldown reduction. With Jax, it allows you to keep Leap Strike ready for you to use to chase down enemies and keep up with those who've ghosted.

Greater Quintessence of Evasion - Ahhh, dodge. We meet again. Obvious quintessence is obvious.

The masteries are mostly in Offense, because it increases his already massive damage. Defensive masteries in Dodge are outrageously effective because, as stated before, Jax relies so much upon his dodge for stuns and survivability. The Nimbleness also helps him chase runners or run away from a gank if needed. The enhanced Exhaust helps significantly more in both occasions. The masteries are generally interchangeable depending on how you play, just make sure you keep the dodge.

Ninja Tabi - Obvious choice here. This is the only item currently on LoL that gives dodge, since they nerfed the Phantom Dancer.

Guinsoo's Rageblade - A MUST HAVE. Gives both Ability Power AND Attack Damage, both of which increase your damage output immensely, as all of your skills rely upon them. Also, it's unique passive stacks with your Ultimate, giving you amazing attack speed in a fight. Not to mention that each stack gives you more Ability Power, which your passive then transfers to HP.

Hextech Gunblades - Spam as much of these as you can. They give amazing Attack Damage and Ability power (which with your passive gives you HP), and the 20% Life Steal and Spell Vamp helps tremendously in keeping you alive during fights. Also, as I said in the introduction, if needed you may want to substitute one of the Gunblades for an anti-tank item, but that is up to you. (I would recommend Madred's Bloodrazor or Last Whisper) With that Spell Vamp and your ultimate

Don't worry about buying HP items, because Attack Damage and Ability Power items are effectively HP items. Your passive transfers quite a bit to your Health. I've had 3k HP with this build.

Your first priority is to get Q, W, and E to level 1. The next is maxing Leap Strike ASAP. Each consecutive level reduces its cooldown DRASTICALLY. This is outrageously helpful in dealing extra damage in a fight and chasing people down when they run from you (which is inevitable). Its level one cooldown is somewhere around 13 seconds, and can be more of a nuisance than anything else, so get that up. Empower and Counter Strike can be leveled as you see fit, depending on whether you need stuns or more damage. Just remember the Counter Strike passively increases your dodge, and can be just as helpful as extra damage. Also, if facing any sort of magic damage character, it's always wise to activate your Ultimate when fighting. The increased Magic Resistance has saved my life many times, and can help keep you alive. Your ultimate passive still works while it's activated, so don't worry about that. You still deal epic damage.

Exhaust and Ghost. Pretty much self explanatory. Exhaust can be used to chase down, run away, or turn a fight with another damage dealer your way. I find Ghost useful for getting to my teammates when they're being ganked or running away if I'm being ganked. You can really use whatever you want, but I find these to be the best.

In the early stage of the game, you suck. Don't try to ace the team or do anything stupid. You don't get powerful until you get your ultimate and your Guinsoo's Rageblade. Play conservative and careful in the beginning, then release your anger upon the other team later in the game. Trust me. They'll pay.

Something you might want to keep in mind is that Leap Strike doesn't have to be on an enemy. You can use it to jump to an allied minion to escape a gank, or leap out of the brush to scare people away. Something else you might like to do is make sure you activate Empower before you Leap Strike. This adds all of the extra damage to your Leap Strike. One time, with this build, I hit over 1000 dmg total on the squishy Teemo. about 570 dmg from Leap and about 500 from the Empower tacked onto it.

Another thing that you can use to your advantage is enemy minions. See if you can fight the other champions next to their minions, because with their minions attacking you, you have a lot more dodges while you're fighting, allowing you to pretty much keep your enemies in a stun lock. Also, try to attack minions before you engage the enemy champions, that way you can keep the stacks on your ultimate and your Guinsoo's so you have max DPS when you start attacking. If you do this, you should be able to melt your targets easily.

That's it. Follow these guidelines (more or less) and your name will be feared all over Runeterra. So good luck, have fun, and KICK SOME ***!