Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This is the second guide that I have made.
Renekton is fun to play, and a beast if played correctly.
Doran's Shield to start off, nice hp regen, armor and health.
After that you go for your boots and Brutalizer. These 2 items will give you a good chunk of cooldown reduction and more armor penetration, yay.
The first build represents longer games, and the second is one that I use in shorter ones, ie: 3v3.
The best starting skill is Ruthless Predator. At level 1, 1 auto attack followed instantly by your W provides 3 hits and a stun, for a huge chunk of damage.
After 1 point in that, pick up you slice and dice so you can slice in, auto and stun, or just stun, then dice back out. It's best to slice in with 50+ fury. In rare occasions, I take Q 2nd if I need the health asap.
At level 3 you should have 1 point in all 3 skills. Your harassing should continue as long as you don't put yourself in a dangerous position. Slice in ---> Auto ---> Stun ---> Auto ---> Cull of the Meek ---> Dice Out. If you just want a quick harass in and out it would be more like: Slice in ---> Stun ---> Auto ---> Cull of the Meek ---> Dice Out.
A note: always Slice through the creep waves so that you will have your Dice. It is very easy to harass in lane if you have control of the bushes. You can Slice right out and commence with your combo.
Using your Ultimate: There are different circumstances in which you should use your ultimate differently. If you are going for the kill, its fine to just up and ulti, but you should do it when you are in range to kill, otherwise they will just run.
If they are tower diving you, you can use it as a nice little heal (300/450/600) hp, and then smack them with a stun, and Cull of the Meek.
Another situation is if you are ganking for another lane, you can preemptively use your Ultimate while waiting in the brush, to build up fury. This is a good strategy because it turns your .75 second stun into a 1.5 second stun.