Hey, everybody. This is my first guide on Mobafire, and it looks like we're lacking in the all-AD Renekton department. So, I thought I'd rectify this situation. First of all, let me say that I'm writing this guide from the view of a solo-queuer in normal 5v5's, so we're mainly assuming that your team is a bunch of self-absorbed idiots that scream, "NOOOOOB OMG WTF NOOB ****.." anytime anyone on your team dies. Now, I know that isn't always the case, but this guide is going to emphasize the lone-wolf queue style.

Renekton is NO LONGER a tanky DPS. Yes, you can still build him that way, but he won't be dealing out as much damage as he used to. His base damage on his spells got nerfed, but his AD ratios were increased. Yeah, that means this croc is going to hit like a ****ing truck when you build him right.

Pros!

-Strong AD capabilities
-Great chaser/runner
-Lots of lifesteal to stay in lane
-CC a Kat who's trying to spin
-Great AoE damage in team fights
-Holds the sexiest Galactic skin out there
-Ridiculous Armor Pen with this guide

Cons.

-Susceptible to focus fire and CC
-His brother is a librarian
-His weapon should be larger

Renekton is an AD champ. Use the ArP marks, or go back to licking the window during your bus ride.
Next, I use dodge seals to synergize with the defensive masteries for a near 7% chance to dodge. It doesn't sound like you'll be dodging very often, but, for me at least, it seems to happen often enough that it's useful.
For glyphs I get CDR. Along with Ghostblade and CDR boots, Ren sits just under the CDR cap. There are some diehards out there that think the CDR cap is a must-have for Renek, but those are the same dumbasses that are still building him with sunfire/warmog's.
Last, ArP quints make the enemy **** their pants the first time you hit them.

LOL OFFENSIVE MASTERIES AREN'T EVEN GOOD LOL.
Please get back to your seventh grade keyboarding class and away from my guide. The only advantage defensive masteries has is the 4% damage reduction. However, when you build Renekton offensively, your lifesteal capabilites will more than make up for an extra 4% of damage here and there.
I take the offensive masteries mainly for the extra crit chance/crit damage to help out our Ghostblade, and for 6 more ArP than we'd have without them.
Then, I drop into the defensive tree. If you're wondering why I decided to get more MR than Armor, I'll tell ya why.
Once you get a good Renek build going, hardly any melee are going to be able (let alone want to try) to stand toe-to-toe with you.
It's true. I've had Tryndamere's run from me when I'm using this build because they'd rather not risk me stunning them before they get a chance to ult, and have me use their skull as a cutting board.
Now, when some genius decides he thinks it would be a good idea to 1v1 you, we've got that dodge chance. He'll start whacking away, only to realize he's missing a few shots here and there, and that's not helping his overall damage. Here you are with ****-tons of lifesteal healing back the damage he does, anyways, and he starts to run. Little does he realize those dodges are making you even faster, and you won't have to waste a flash to Ruthless Predator him and send him to oblivion.

If you ARE set on reaching that CDR cap, by all means go into the utility tree. You won't lose THAT much damage, and you'll be a little quicker/have a shorter flash CD, but it's always been my preference to have that extra ArP/Crit chance.

Probably the only reason you clicked on this guide in the first place, so I won't disappoint.

Doran's Blade- I choose this over the shield, because I feel the damage and lifesteal make up for the lack of 20 health and a bit of armor. Take the shield if you want, or you can start with boots and 3 health potions. Just play a little more carefully if you do grab the boots, since you'll be down 100 health and damage/lifesteal.

Ionian Boots of Lucidity- CDR boots. You're using your skills more often = more stuns/damage/healing/chasing/EverythingthatmakesRenektonawesome. Get these boots. If their team is pure CC/AP, you can grab those Merc Treads we all love instead.

Phage- I don't upgrade Phage in this guide, nor do I in-game. With your W applying on hit effects, and a Youmuu's Ghostblade to buff your attack speed, chances are you'll be putting the slow on them before they realize they should be running from you as fast as possible. Phage also give some health for survivability and some damage that isn't bad for early game. However, if you complete all the other items in the build, upgrade it to a Frozen Mallet by all means.

Black Cleaver- You know how people used to swear that Sunfire was "THE ONLY ITEM RENEKTON NEEDS"? Well, that's been replaced. Cleaver is just too amazing on Renekton. It gives us some tasty attack damage, some attack speed to charge our fury bar faster, and its on-hit effect goes GREAT with Ruthless Predator. Once you have a fury-charged W up and a Black cleaver, you'll drop that on an opponent and they'll realize they suddenly have 45 less armor than they should, and that you're hitting them like a 12-foot tall bipedal crocodile with an axe should.

Youmuu's Ghostblade- Crit chance, ArP, CDR, and an active for move speed and attack speed. What's not to love?

Stark's Fervor- An aura that helps your fellow AD teammates, a nice amount of lifesteal and attack speed, and some more ArP for you, kind sir.

Bloodthirster- Even more lifesteal. You know, in case your CTM, and Stark's just aren't doing it for you. Also, up to 100 damage to shove into your enemies' faces.

Yeah, I max Ruthless Predator first. This is your W, and your bread and butter. It can be used offensively and defensively, and hurts like hell regardless. Especially early game, this beast will drop your enemies' healthy by at least 1/3, and stun them to boot. Now they're losing health while you and your lane partner beat on them, and you know they'll be sprinting back to their tower, possibly wasting a summoner spell in the process.

I don't get Cull The Meek first, simply because I get Doran's Blade and you hit level 2 fast enough that you shouldn't need a ton of lifesteal off the bat. Also, you shouldn't be trying to wipe out minion waves crazy fast at the beginning of the game anyways, so it's not super-useful.

Yeah, Slice and Dice is good, but isn't really necessary until you really want to get some kills. Auto attack some minions until you have 50 rage, Slice over to your lane enemy, smack him with your W to show him who's boss, Q, then Dice back out.

I go Flash and Ignite for my summoner spells just out of personal preference.
Flashing over and smacking some kid with your W to initiate is usually unexpected, and might get you a kill while he's scrambling to figure out what to do. Plus, if he might get away, Ignite his ***, /t, and watch him burn.

Other Viable Summoner Spells

Exhaust - Yeah, you can. I like to hop into the jungle to get red buff, and I always W AoE ults to stop them, so I like ignite over it.

Ghost - Youmuu's isn't making you move fast enough? Go for it. If you want to be Usain Bolt - Crocodile Edition for a few seconds, be my guest. Take the point out of Nimbleness and spec for Improved Ghost if you're going with it, though.

Spells I probably wouldn't use.

Clairvoyance - I like it on TF and some other support champs, but if Renekton wants to know if someone is in a bush, Renekton Slices into that bush and ***** on anyone stupid enough to be spying on him.

Teleport - Yeah, why not. If you're an always-in-the-action type, get on it.

Cleanse - If you're getting CC'd to the point where you need cleanse, chances are you're going to die quickly regardless, but you can take it for those tricky 1 on 1's.

Fortify - It's always funny to have someone tower dive you, only to get smacked with Ruthless Predator and popping Fortify. The tower turns into a gatling gun, and they're filled with so much regret they just might rage quit.

Heal - Self-explanatory. If you're that aggressive that you need it, take it, or learn to be patient.

Summoners spells I wouldn't use on Renekton.

Clarity - HAHAHAHAHAHAHAHAHAHA.

Revive - Yeah, I like 9 minute cooldowns.

Rally - Doesn't add enough damage to really make a difference or make it better than any other summoner spell.

Smite - Jungling and I don't get along unless it's later on in the game and the monsters only fight me because they're programmed to.

I play my Renek the same why I play nearly all of my AD champs. I try to make armor as little a factor as possible when it comes to my damage. As you can see in my items/runes/masteries, I want to hit tanks like they're a ******* Soraka Bot. With Stark's up, and three Cleaver stacks, you're looking at an opponent with a 100+ armor deficit. That's enough to turn anyone without armor items into hot butter, or to completely negate the Thornmail they picked up after you'd wrecked them for the seventh time.
Also, as with every champion, play smart, for God's sakes. I don't want you coming back to this guide whining because you're at a health/armor/MR deficit. You know your role is to go in and wreck some face. Your lifesteal, along with good placement for a fury-charged Cull the Meek should keep you alive through the end of a teamfight, or at least long enough for you to severely cripple their ***es, and let your teammates do their janitorial duties.

Some tips:
-Save your W in team fights for when anyone with an AoE ult tries to take out your whole team. Stun Kats/Nunus/Karthuses before they can do some real damage, and your team will win that team fight. If they have more than one AoE damage dealer, play it smart and stun the biggest threat.
-Use your fury WISELY. Use that fury-charged cull the meek when there are a ****-ton of minions/enemies around for the maximum heal/damage.
-Open up with a fury charged Slice and Dice, don't use your fury on it AFTER you've already dropped their armor with cleaver. Taking out that 15% before dropping it by 45 has a nice impact on the overall armor they'll be down by. Say their tank has 200 armor. (.15)(200) = 30+45 from cleaver afterwards, making them drop 75 armor. However, when you Slice after you've stacked Cleaver on them... 200-45 = 155(.15)=23.25 45+23.25= 68.25. The more armor they start with, the more armor you'll reduce when you Fury Slice FIRST.