A very very tanky Renekton build wich is intended to be durable through teamfighs and such with no problems at all.

But still he can do alot of damage.

The items that I recommended are pretty simple. Renekton is usually played as a solo top champion and if you are agains someone like Vladimir or Poppy you could forget the Ionian boots of Lucidity and go for Mercury's Treads. The Yoummu's Ghostblade is mostly for armor penetration and for its Active ability to give you attack speed and movement speed. The doran's blades are just something I like to take in early game for some extra health and attack damage to take advantage of Renektons early game dominance.

Because I build such tanky items I think it would be better to put most of the mastery points into offence. Dont worry about that because Renekton can take a hit.

I always max Renektons Q first becuase its his main source of damage but I take the Ruthless predator at Lv 1 mostly because I stop for a gank with my teammates for first blood. The slice and dice is left at Lv 1 and maxed last because its only used to dash towards an enemy. You can use the combo of Slicing to the enemy making sure you hit him with slice, quickly use your Q for alot of damage,hit Ruthless predador for the stun and and use the second part of slice and dice to get away safely. If you can make your fury bar higher than 50% fury tha would be painfull for the opponent.