Hi this is first good build on mobaFire.
This build is about Renekton, because he is awesome to play with.
Specially this build is for ranked games.
If u like this build comment and vote it =].

Rune choices:

Greater Mark of Desolation Your a physical champion and these happen to be the best runes out there for you.

Greater Seal of Evasion More survivability, especially in combination with 'Nimbleness' in the masteries.

Greater Glyph of Cooldown Reduction Big crocodile, big cooldowns, so why not reduce those by an extra 5,85% ?

Same as goes for the marks.

Masteries:

I went for a standard 21/09/00 DPS mastery build. If you don't happen to have dodge runes you could drop the points in Nimbleness and Evasion, and put those into Alacrity, Archaic Knowledge, Hardiness and Improved Ghost (if using Ghost offcourse).

Ghost and Exhaust
Ghost makes for excellent chases and escapes, wich is usefull because your E Slice and Dice might be on a long cooldown.
Exhaust: We put a talent point into this one, wich makes it even lowering armor and magic reststance and increases it's duration. Great for ganking, but also good for getting away.

Other choices I would recommend instead of these:
Flash Somewhat of an extra E, but with a longer range. In 3v3 this makes u able to 'jump' the thick wall above the lizard, and in front of the bases.
Ignite extra DPS with this DoT, possible counter for Dr.Mundo/Tryndamere/healers.

Reign of Anger Reign of Anger is Renekton's passive. It explains the new Fury system, where each of your attacks or abilities that hit enemies will generate Fury. All of Renekton's abilities are free, but they gain additional damage and effects when activated while Furious (above 50 Fury) (aside from his Ultimate). Reign of Anger grants you extra Fury generation when under 40% health, making him much deadlier at lower levels of health. Ideally, however, team fights should be decided when you're stomping around in Dominus form, and you shouldn't need the extra Fury generation that much in most scenarios.

Cull the Meek(Q): Renekton swing his blade, dealing damage to nearby enemies and healing for a portion of the life dealt (more health gained if you hit champions). Fury Bonus: Heal amount raised dramatically. This is your first harassment skill, and it will make you lane longer by healing yourself. Make sure you hit as many champions/minions (max. 5) as possible with this skill in order to gain more health.

Ruthless Predator (W): Renekton's next attack swings twice, dealing a portion of his weapon damage, stunning his target briefly and applying on-hits each time. Fury Bonus: Renekton's next attack swings three times, dealing a huge portion of his weapon damage, stunning his target greatly and applying on-hits each time This is your second harassment skill, your main damage skill, and will therefore be maxed out first.

Slice and Dice Slice and Dice is your E, and it gives you incredible mobility both in the lane and in the jungle. You can use this to dash over walls to chase or to run away, while you can also use it for the same purposes in lane. Rarely will you use this skill for damage, at least not until the late game, so you max this last. However, the mobility provided by this skill is superb, which is why we get this right after getting Ruthless Predator, to make our combos much stronger.

Dominus Dominus is your ultimate. It essentially turns you into a giant rapist for the next several seconds. You deal increased AoE damage, have a larger range with your attacks, and generate Fury passively while Dominus is up. This is most useful in a 1v2 lane or in a team fight, since it literally turns you into a monster in battle. Always save this for when you are sure a team fight is underway - the chaos you will wreak is substantial.

Pros
*No mana
*Potent tanky DPS in mid and late game
*Nobody picks him in ranked.
*Good Farmer

Cons
*Sometimes squishy early game
*If you play ranked, and pick renekton people will be yelling @ you.
*High CD

First start with:

dorans shield + Health Potion

After that rush for Giant's Belt

Than Ruby Crystal and finish your Warmog Armor

Now you go for Atma's Impaler

Next item depends how you're doing now.
if u want some attack buy: The Brutalizer
Alot of AP in enemey go for: Spirit Visage

Sorry i finish it so f***t if i can!