Not Updated For Current Season
This is my way to play Renekton, also knows as Nasus' brother. I choose Ignite and Ghost as Summoner Spells, Ignite for that extra little bit of burst damage, and Ghost to escape ofcourse or to chase down a enemy champion.
First of all I start of with Doran's Blade, obviously for the bonus Health, AD and a little bit of Lifesteal for the beginning of the game, with the money you have left, buy 1 Health Pot. Renekton is a great farmer so you should get much money early game with minion kills. When you reach 900 gold recall for Ionian Boots of Lucidity, you can also go for Berserker's Greaves for better Fury regeneration or for Boots of Swiftness to chase your enemies down. I choose for Ionian Boots of Lucidity for that extra cooldown reduction. After that you wanna save up money for The Brutalizer and later combine the other items to make Youmuu's Ghostblade for the extra Attack Damage and Crit Chance, also the items Active is very handy in teamfights or to chase someone or to run away. Save up money for Frozen Malet, it is a very nice item to chase enemies couse of the item passive (slows enemies on hit) and it gives a big addition on your health pool so it's harder for enemies to get you down. After Frozen Malet you wanna get Guardian's Angel, why you ask? Couse of its awesome passive and for that extra armor/magic resistance. When you get Guadrian's Angel save up money for Zeal and later buy Phantom Dancer, for the extra Attack Speed so your Fury regenerates faster and the movement speed and crit chance are also a good use ofcourse. As a final item buy Stark's Fevor, also another addition for your Attack Speed for a better Fury regeneration and for the extra Lifesteal for you and your team.
If you play against Karthus, you wanna get Hexdrinker instead of Stark's Fevor and buy that before you buy The Brutalizer since it will save you alot of times from Karthus' ulti.
Get your first point in Cull the Meek for farming minions. Renekton is a excellent farmer with Cull the Meek and the Slice and Dice combination. At level 2 give your Slice and Dice a point so you can start some good farming. Level 3 go for Ruthless Predator, after this I usually go for First Blood if I got a burst damager with me in 1 lane. At level 4 and 5 go for Cull the Meek again for better minion farming and bigger damage on champions. You wanna try to get 50 Fury first and then use Cull the Meek since it will give you more damage, and bigger health regeneration on the hits. At level 6 go for Dominus, wich is a very nice Ultimate. It can save you alot of times when someone uses Ignite or when for example Karthus uses his ulti couse when you use Dominos, you gain bonus health. Also you get Fury regeneration and continualing damaging enemies near him. Further in the game max Cull the Meek a.s.a.p and then finish your skills with each level switching from Slice and Dice to Ruthless Predator, for balancing your damage out.
Engaging enemy hero's or teamfights
With Rekenton you are a great addition in teamfights since Cull of Meek hits all enemy champions around him. When you engage a teamfight use Dominus first to damage all nearby champions every second. Slice and Dice trough as much enemy champions as you can and try to hit as much champions with Cull of Meek as possible. You wanna save the 50 Fury up for Ruthless Predator becouse it will stun the enemy champions for a longer time and will hit them 3 times instead of 2 so it's a great help for your team to kill the focused champion. When you play 1v1 Rekenton is also good, just burst them down with Slice and Dice and then Cull of Meek. Also here you wanna save up the 50 Fury for Ruthless Predator for the extra 3rd hit and additional stun time. If you think you won't make it without Dominus, just pop it.