*first thing's first, the stats shown above are unaccurate. With maxed out Warmog's you should have 3572 HP. This means that your attack should be 270ish which is incredible.
*I give some credits to Fecesnugger who came up with such an idea. Myself for testing and analyzing this idea.

Alternative Summoner spells include ignite to finish off enemies, or cleanse to get rid of all your troubles. You may take flash as well so you'll have a "double flash."

As usual, I will do a brief Pro and Con on Renekton based on the benefits of this build.

Tank Renek

Pros
Tanky
Decent Farmer
Harrass without dying

Cons
No damage output
After you stun one person, no more CC

You can tank everybody and that's great but they don't even bother to deal with you because you can only stun one person and then what? You start tickling them with your minimal DPS?

DPS Renek

Pros
Great DPS
Great burst

Cons
Quite squishy for a melee champ even with ult
Exhaust or CC=bye bye

This build, you may be able to dish out tons of damage but i can almost guarentee that you will die after killing maybe one person in a teamfight. When exhausted or CCed you can't do anything

Tanky DPS Renek

Pros
Nice damage output
Very Tanky
Good skill and item synergy
Great farmer

Cons
Lacks early game survivability
Starts off with pretty high CDs

Great Pros, Cons can be negated middle to late game, so renekton is actually a great champ right now. Not only does he have a good burst, but with this build he has a nice DoT as well (damage over time)

Cull the Meek - great skill for farming, for surviving, and for damage since they buffed it. Use this as often as you can since you have no mana cost. Not only does it add fury but it has quite a large AOE. (he spins once where he is and deals damage to units around him. You can move will spinning)
With 50 fury, it does additional damage and lifesteal

Ruthless Predator - you're single target massacre skill. This does amazing damage PLUS a nice stun. Great synergy with slice and dice. (This procs your next auto attack to stun and slash them twice)
With 50 fury it slashes 3 times and stuns for a longer duration

Slice and Dice - Damage is lacking, but it's a small flash, and if used correctly can be a double flash since slicing an enemy procs the skill to allow you to "dice," which is the exact same thing as slice. (You dash a certain range dealing damage along the way)
With 50 fury, your dice will shred some armor off the target plus additional damage.

Dominus - your ult, an amazing ult at that. It's like Nasus', you gain HP and you grow bigger giving you a longer reach. What's amazing about this is that it deals magic damage to enemy around you/second. At max rank this is just insane. With your high HP you don't need to worry about getting killed. (you turn bigger and there'll be dark energy swirling around you.)

I went with a standard armor pen, dodge, and CDR runes.

Armor Pen Marks - increases your damage
Dodge Seals - more survivability for your early game
M res Glyphs - since there's not much mres, i've decided on m res glyphs
Armor Pen Quints - same as marks

I did a 21/9/0 mastery build because he gets good damage from the offense masteries, and some CDR. On the other hand, the defense masteries just add to his tankness

- Like I said before, he lacks early game survivability no matter what people say about his skills. You may be able to slice stun cull dice but if you get CCed, you're dead.

- CDR is great for Renekton because of his lack of MP, makes your skills more spammable.

- Helps with your survivability alot. Additionally, you get more gold added to your nice farming skills which lets you get items alot quicker. This can later be built into Randouin's Omen which is quite nice for Renekton.

- This is the main different about this build than all other builds. You gain a massive amount of HP letting you stay alive. This is effective with the next item.

- I can say that this and Warmog's are your main items since Warmog's gives you some tankness and this boosts your damage by a ton because of warmog's and boosts your armor and crit chance.

- With the remake, this item is just smexy, what can I say. Armor pen + damage + attack speed = smex. Great for your DPS

- This is your main armor item. It's a really great item. It has CDR, armor, HP, and it's active shuts down DPS champs and let's you chase really easily. Built out of your HoG

- Finally for a bit more CDR, damage, crit, and attack speed you can add this item.

Situational Notes

You may have noticed that this standard build is based off of if the enemy is high on DPS. SO....if the enemy is high on AP, Banshee's Veil or Guardian Angel instead of building the HoG into Randuin's and possibly removing either Youmuu's or Black Cleaver might work for you.

Mercury's Treads - If enemy is high on CC

Hints, Tips, and how to play Renekton effectively.
Laning partners that you should be looking out for:
Ranged champs to back you up if you're getting harrassed.
Support Champs to help you survive and such.
Extra stuns/taunts are nice too.

Early Game
Get a doran's shield and head out to your lane. You start off with cull the meek because it lets you farm and stay alive. You then get slice and dice because this is one of the only ways to get in there, stun then get out in one piece. Play smart. Know when to harrass and know when to be defensive. Use Cull of Meek to farm and help you heal up. Be weary of MIAs because slice and dice just isn't enough to help you get out of it. Always last hit so you don't push the lane up.

Mid Game
Kay. So you should have some basic items by now. Should be at your HoG or Warmog's or maybe even Atma's. You can gank at times since your skills have a pretty nice damage output and stun. Your ult really helps too because of the extra damage, HP, and reach. In teamfights, don't be afraid to be in the middle of things because of your ult and Cull of Meek. Remember to FOCUS THE PEOPLE WHO PUTS FORTH THE MOST DAMAGE. (THE CARRIES.)

Late Game
By this time you should have mid 200 damage, 3k+ HP and just absolutely dominating. Push push push, kill kill kill, tank, tank, tank. not sure what else I can say. Don't be afraid to get the elixir of fortitude sometimes.

Tips
*You guys should know that the basic harrass combo is slice in, stun, cull of meek towards your base (since you can move while spinning) and then dice out.
*You guys should also know that slice and dice allows you to go through walls and such, but be careful because really thick walls are impenetrable.
*Use of Fury: Ok, during laning phases you should be using your 50 fury on cull of meek because of the farm, and life steal. During teamfights and 1v1s and 2v2s and such you use it on Ruthless Predator because it deals terrible terrible damage with a longer stun. But if you're dying and there's a considerable amount of enemies around you, use cull of meek.
*Ruthless predator is both offensive and defensive
*I wouldn't consider using slice and dice with fury because really it's quite a waste because the damage isn't that nice and your runes/black cleaver should be enough.

I'd say Renekton is a fun champ to play now that he doesn't suck so hard. He has nice artwork too so he looks like a cool champ.

One of the games where I dominated. I know it's only one but all the match histories of renekton for me are gone and this is one of the two left. My other one was a victory with a score of 7-7-6. If requested I will play more and add more.