Skarner is a very flexible and fun champ to play.
That is what this guide is about: four main possibilities of playing him:
HYBRID + AD-DPS + JUNGLE + TANK

My guide is orientated on the following priorities:

• Survivability
• Teamplay
• offensive effectiveness
• successful and quick jungling
• FUN, FUN, FUN

Have fun reading, and please give me your honest opinion before downvoting.
Thank you!

With this guide the list looks like this:

Pros:

• not squishy
• good chasing
• good initiating
• very flexible with ingame item-build
• good Teamplay with ganks, wards, Teamfights
• Flexibility in role: Jungle, Solo, Double-Lane, Tank

Cons:

• no massive damage early game
• no burst damage
• not the best jungler compared to Udyr or Warwick
• maybe a little bit too mana dependent (especially early game)

Please don't blame me for my rune and mastery choice. In my opinion runes and masteries are specific for every person's style of playing. For me, this combination is the best, because of the defensive boni. But feel free to use your own combination, which fits to your style of playing.

RUNES:

For Seals I always use Greater Seal of Armor

For Glyphs I always use Greater Glyph of Scaling Magic Resist

Their defensive boni are really significant!


For Marks I usually use Greater Mark of Desolation
But if you are building Hybrid you could use Greater Mark of Magic Penetration of aswell.
If you jungle Greater Mark of Attack Damage is a also a very good choice.

For Quints I normally use Greater Quint of Alacrity.
But if you love the extra life I recommend using Greater Quint of Fortitude.
( I don't know why the Quints have no image, it does't work )




MASTERIES:

Finally we come to the item choice.
This is the part where the difference between Hybrid, AD-DPS, Jungler and Tank is made.

As you can see almost every build startw with Doran's Ring.
I'm a fan of this item, and without it I get mana problems with Skarner. If you don't - use another ... maybe a Sapphire Crystal for an early Sheen.
But I think ...

• 100 HP
• 5 manaregeneration
• 15 AP damage

... is just perfect for Skarner!


Items for Hybrid:

Items for AD-DPS:

I like the combination of four cheap but effective items:

Bilgewater Cutlass + Phage + The Brutalizer + Zeal

After that I build them to the items listed and transform into a tanky chaser!
Items for Jungle:

As you can see the Jungle items are not complete.
That's because the differ from game to game:

I use Mercury's Treads + Wriggle's Lantern + Trinity Force as core.

After that I build, what my Team needs. A quick look at the scoreboard tells me what my Team is missing, or what is best against the enemy team. Usually i stay with my favourites like Hextech Gunblade or Frozen Mallet.
But if I need to be Tanky Aegis of the Legion or Guardian Angel might be better!



Items for Tank:

This one is easy.
I always max Shattered Earth first, because i want to be a terrifying chaser! :P
One early point in Ixtal's Impact gives me decent heal,
and one in Seismic Bastion gives me the necesseary speed and AS to chase

And oh, of course put a point in your ultimate whenever possible!

This again i very specific according to your style of playing.
I love Flash and Exhaust because both can be used offensively aswell as defensively.

With Exhaust and your Impale you can diminish the damage output of two of their DD's in Teamfights which is extremely helpful for your team!

And if you jungle - Take Smite, of course.

Your role in a 5v5 teamfight is not an easy one.
I usually try to put my Exhaust on the strongest AD Carry and hit the next best DD with my Impale.
After that I chase one of them as long as I can.

Outside of a teamfight I try to chase anyone I can. :P

I'll update this section, when I have more experience... :D

Well, this was my guide.
It is not perfect yet, so don't hesitate to give me tips and critque.
I'll try to update as soon as possible.

Thank you for reading!

Have fun Playing,

Yours Meerkatz13