Well, as you know Renekton is a Bruiser, I've been playing Renekton ever since he came out, playing normals forever trying to get him down. Going against other Renektons shutting them down, because they all go deep DPS. And i got a little more tanky than DPSish.

I also, tried tons of different rune combinations. And to me, this is what suits him well.

I've been playing Renekton in Ranked Matches. To be honest if you play him well, he can carry you to higher ELO. I've always been Carry/Tank.
Hes a great harasser/farmer/pusher and at times, counter-jungle.
I always lane with Renekton either top solo(with a jungler) or the 2v2 lane.

PROS: Hes a really great farmer and with those heart of golds i put up there make items a breeze to achieve.

CONS: You might get Renekton balls; where you want to go balls deep in the team and rape.
Its cool and all, just hope you have the team to back you up.

One of the coolest things i like about Renekton is, the harass.
What i did(and was pretty fun)
is Slice(from Slice and Dice) through minions and at the same time,
try to hit the enemy with it,
or just Ruthless Predator them,
Cull the Meek and Dice(from Slice and Dice) back.

Ok the items as show are a [Doran's Shield] to start off.

Then when you go back, get [Boots of Speed] and A [Heart of Gold] of if not some pieces of it and some health pots.

Then [Mercury's Treads], finish off [Heart of Gold] or if u can get 2.

Then [Hexdrinker] And once you have [Hexdrinker] is actually when u can get a little crazy popping your ult focus someone down with your ult + Ignite, Tanking a big team fight n such.

Then after that is good ol' faithful [Sunfire Cape]. It goes really well with your ult. And overall owns.

And also, Somewhere along the lines you want to sell your [Doran's Shield] most likely to finish off an item.

You're also wondering why i probably put 7 completed items besides the [Heart of Gold]s.

Because, if the enemy team is AP heavy get the [Spirit Visage](Also goes well with your passive and with healers on your team d:D) or if the enemy team is AD heavy, grab a [Thornmail] And then sell 1 [Heart of Gold] to finish one of these items.

Then [Randiun's Omen].

And if the game gets longer look like jesus and buy all the Elixirs [Elixir of Agility], [Elixir of Fortitude] and [Elixir of Brillance]. And why not [Oracle's Elixir].