Hello! This is my first build. I bought Skarner a few days ago and have been playing quite a few matches with him. This entire build is what I have been using, so it's all my opinion, and other builds may be MUCH better than mine. So go easy please :P As i've seen phreak play him on the champion spotlight, i felt making him tanky left out quite a bit of his damage output. This build may seem very odd, But it does work for soloing most champs. But be warned, This is an endgame build, and is very hard to use until the right items have been acquired. What this focuses on is auto attack damage. Able to hit extremely high and fast endgame. When i first tried this, I instantly realized that it felt like I was playing Master Yi(Auto attack damage).
Skarner changes from a tanky dps, To more like a single target Nuke. Especially if your fed.

For red, I take 9 greater marks of furor, simply because it adds to the massive crits.

For yellow, i take 9 greater seals of replenishment. Simply because early game, his mana pool gets depleted VERY quickly. This helps stay in the lane quite a bit longer.

For blue, I take greater glyphs of alacrity. Attack speed will help get the first blood.

For Quintessences, I grab 3 greater quintessences of Furor. Just adds quite a bit more to the crits, very useful.

For masteries, i take a 22-0-8. The crit damage, attack speed and cooldown reduction are too good to pass with this build.

The eight in utility are mainly for ghost movement speed, Health and mana regen, And experience gained in the lane.

Alright. For this particular build, Skarner needs expensive items, and quite a few. Don't worry about the prices, The game usually ends around the time when i grab the bloodthirster. Adn because Skarner is a good farmer, it goes pretty fast. After you get the phantom dancer, you can do some serious damage. After that, it goes up dratically.

First, I start with a Doran's Blade. I take this instead of A vampiric scepter, because Skarner is VERY squishy early game. And because the first skill I grab is one that gives back HP.

Next, i work towards the Berserkers Greaves. Attack speed and movement speed are too essential to miss. Especially against ganks.

Zeal is the next thing to pick up, Get some attack speed and crit. It helps last hit minions, And with the items in this build, you will need to.

After a little farming, A B.F. sword is the next item. This will be used for infinity edge.

Infinity Edge is next. -amazing.

Phantom dancer is right after the Infinity edge. Crit, attack speed, and movement speed. Crucial piece.

Another B.F. sword, This time, making a black cleaver.

Black cleaver. Just makes the crits higher.

At this point, you can sell the Doran's Blade to buy a Vampiric Scepter. This will go into a Bloodthirster.

A Bloodthirster, Lifesteal will help against pretty much anything. Plus the other stats of course.

And last, A Madreds Bloodrazor. More stats!

Pretty scary.

Passive- Energize.
Basic attacks lower the cooldown on his abilities.

(Q)-Crystal slash
Not really going to be that useful in this build. It does not get powerful enough the take to do any real damage with this build. But a useful AoE for other AP builds. Just grab it when you cant get anything else.

(W)-Crystalline Exoskeleton
Gives a shield that absorbs damage, gives attack speed, and movement speed.
This is the biggest piece of this build. You will want to max this early. It is very good for chasing and escaping, as well as burning a single target.

(E)-Fracture
Launches a projectile that passes through targets, and when Skarner attacks them gives health back. I take this from level 1, simply because it is a very good Harassing tool, and gives you more sustainability in the lane early game. Hard on mana though.

(R)-Impale
Skarner impales the target, doing damage, and dragging the target around for 1.5 seconds.
Great utility with this move. Doesn't do much damage with this build, But can turn a 5v5 into a 4v5 very quickly. Just wait for one to over extend, And you and your team have a kill. Very useful. Grab whenever possible.

For this build I take ghost and flash. What Skarner lacks is a closer and mobility. These can be used offensively, Or defensively. These are the best for escape a gank from mid, or anywhere.

Pros-
Single target nuke late game.
Hard to catch.
Can jungle for buffs early.
Ganker.
Ult is very useful for anything really.(shutting down other champs during their ults)

Cons-
Very squishy.
Easily CC'd.
Usually focused, making him die first in large teamfights.

Not the best farmer early game, But late game, Very Very good.