Nasus - Off Tank
http://www.mobafire.com/league-of-legends/build/nasus-Off-Tank-15094

Xin Zhao - Jungle - Carry
http://www.mobafire.com/league-of-legends/build/xin-zhao-jungle-carry-18909

Renekton - Look Mommy its a - OH ****
http://www.mobafire.com/league-of-legends/build/renekton-look-mommy-its-a-oh-****-51727
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Hello everyone! This is my first build that I have made.
I give some credits to HeAt because I used his build to start off and eventually made this one by altering his build.

Pros
-High amounts of damage
-Amazing at chasing people
-Very hard to be KS'd
-Great at escaping
-Takes out squishy people in matter of seconds
-"This unit is a flippin ninja"
-Can take out towers easily

Cons
-Squishy and Hard to play early game
-You'll be targeted a lot because of your high damage
-A lot of the items cost a large amount of gold.

Summoner Spells
Flash: This spell is great for escaping a gank and chasing people who have natural jumping abilties and jump over walls. Although it has a high cooldown, it is highly useful.

Exhaust: This spell is great for people who need to hit you with physical attacks and could probably kill you. It will blind them, and slow them, giving you enough time to nuke them and most likely kill them.

Core Items

Boots
The boots are up to you. If you want extra magic penetration get Sorcerer's Shoes. If you want to move faster get Boots of Swiftness. I personally prefer the Ninja Tabis for dodge, but if they have a high team of disables you can get Mercury Treads.

Early Game
Grab a Amplifying Tomb and a Health Potion and go to your designated lane. This will give you some more early game damage on top of your runes. Use your Mark of the Assassin skill to last hit creeps and harass enemy champions. Stay in the lane until level 6 or until you feel like you've got enough money. (I usually stay in the lane until 3k gold) Once you head back to your base get the Mejai's Soulstealer and start to work on your boots.

Mid Game
Mid game will usually start as soon as turrets are starting to be taken down and ganks are starting to happen. This is a crucial phase for you to get your Mejai's Soulstealer up to max right away. Once you have enough money you can start to work on your Zhonya's Ring. This item will make you hit like a beast. By this time (assuming that you've ganked with your team and have gotten kills) you should have at least 10 stacks on your Mejai's Soulstealer and be dealing a large amount of damage. Get your Hextech Revolver so you can have some spell vamp and stay out in the field more.

Late Game
By this time you should be fighting as a team. Aim for the squishy champions first cause they'll die in a full combo of skills. (maybe a little more) You will most likely have an extra 100% magic damage added to your normal hits. You'll be able to take down towers like nothing with this extra damage. Once you get your Rylai's Crystal scepter you'll have more hp and slow. This will make it easier to take down some tanks as well. And if squishies somehow survive your skill combo they won't be able to run. (even though you could still catch them before, now its really no point to run) Get a lichbane to make your Q do even more damage when you do a physical hit. By this time the game should have finished, but if it still continues upgrade your Hextech Revolver into a Hextech Gunblade. And continue what you have been doing.

In no means am I telling you that you will be unkillable if you use this build, because you'll still be able to die if you act dumb.