Hello, all. I don't play ranked, so I can't establish any concrete credentials, but I've played 2500+ games since season 2, when I began, and with my main, Anivia, I can usually win lane against players as high as plat 2. With her, I've had as high of a win rate as 70%.

Aside from Anivia, I play a looooooot of Maokai, both as a jungler in 3s, and a support in 5s. I used to play a great deal of Skarner prior to patch 4.10, when he was severely nerfed. I was so disgusted with the changes that I stopped playing him for the most part, but then Guardian of the Sands Skarner was announced. This is the greatest skin that Riot's released since the Harrowing 2012, which unleashed Haunted Maokai and Zombie Brand . It forced me to get back into Skarner. Having been away from him for some time, and getting a chance to look at him with unbiased, fresh eyes, I discovered that Skarner's still freaking amazing. His mana costs, specifically on his Q, have been significantly lowered, meaning he has to worry much less about mana outside of extended team fights. The slow on his E, which was the only change that I liked back when he was reworked, is amazing. The range, duration, and strength of the slow are incredible. It makes an already insanely fast champion even harder to escape from/catch. His shield retains its UNBELIEVABLE 80% AP ratio, making AP useful as a DEFENSIVE stat on him. Honestly, the only thing that Skarner lost from his rework is the on-hit CDR for all of his spells, although, his Q still has it. The only thing that Skarner's lost is the frequency of his shields.

Also, one last thing: Please, please, PLEASE do not play Skarner as an AD fighter. AD does very little for him, and if you aren't building AP on him, you'd be a LOT better off going pure tank. This is no longer true, as Skarner got some AD ratios added on to him. He'd honestly be a pretty decent hybrid candidate, as well.

OP: Overpowered
AD: Attack Damage
AP: Ability Power
MS: Movement Speed
MR: Magic Resist, magic defense
CDs: Cooldowns
CDR: Cooldown Reduction
AoE: Area of Effect
SS: Summoner Spell
HP: Hit points; health, life
MP: Magic points; mana
CC: Crowd control. League has a bizarre usage of this term. It doesn't mean dealing with a group of enemies, like in everything else. CC in League of Legends is equivalent to status effects (ex. poison, darkness, slow, etc.) in anything else.
DPS: Damage per second, as opposed to burst, which is dealing the majority of your damage in a short period of time, generally under a second or two.

MFSB: Moonflair Spellblade
Vile: Vilemaw

TT: Twisted Treeline
SR: Summoner's Rift
3s: 3vs3; Twisted Treeline
5s: 5vs5; Summoner's Rift
Old 3s: TT prior to the total remodel on 10-25-12.
New 3s: The current TT, with Vilemaw, new items, etc.
"Glass": Little to no defense.

IMO: In my opinion
ATM: At the moment

If there's anything I missed, please let me know.

Pros
Insane chasing power
Four AP ratios, two of which are very high ( Seismic Bastion, Impale)
Fantastic initiator, extremely good ganks
Powerful CC
Versatile: Can tank or carry just by switch his items; scales with AD, AP, and HP (it's hard to find a bad item for him)
Not that item dependent (really just needs MS and HP to get rolling)
Can solo Vilemaw early (those crystals, man)
Low mana costs, so even spamming spells doesn't take a lot out of you
Is voiced by David Lodge

Cons
Short range outside of Ixtal's Impact
He takes a significant hit to stats while fighting outside of his crystal zones, especially early game
Lonely

Details to come.

Skarner excels in extended fights, boasting above average DPS and low CDs. This means that he deals his damage over time, as opposed to in a single burst, but with low CDs, he can ramp his damage up quickly. He doesn't really have much of a combo, but that doesn't mean that his abilities don't have synergy. Skarner can easily outrun people, and either damage them while chasing, or slowing them down and just getting the hell away.

The starting items are purely to help your first round in the jungle. After that, you want some form of Runeglaive. Honestly, every single jungle enchantment would work for him. I used to get Ranger's Trailblazer, but with the insane crystal zone buff, it might not be necessary anymore. Stalker's Blade would naturally be the next choice, but really any of the four should work.
Anyway, you work your way from there with open eyes. If you lack chasing power, get items like Turbo Chemtank, Dead Man's Plate, and/or Enchantment: Alacrity. If you need defense, look into Dead Man's Plate (hello again), Spirit Visage, and maybe Abyssal Mask if you're ahead. While Frozen Heart is an amazing item, you can get its stats elsewhere on Skarner, so I go for other items most of the time on him.
If you're able to stick to people well enough, and can also take hits, the next thing on your checklist is damage. Nashor's Tooth will do things for Skarner that you didn't think would be possible. With just that and Runeglaive, you'll be able to 1v1 all but the most dedicated duelist, not to mention, a lot of your damage is AoE and hybrid, which can make it very difficult to deal with a fed Skarner.

Thanks to your absurdly powerful crystal zones, you can start with golems and take Gift of Heavy Hands. From here, it honestly doesn't matter where you go next. Just get a full clear, keeping in mind that the wraiths, while the weakest camp, aren't within a crystal zone. After your first clear, look to gank a lane if possible, and if not, be prepared to capture an altar and/or go see what the enemy jungler's up to.

Skarner is a tanky AP champ who benefits from both AS and CDR in order to become a great duelist, and MS and tankiness to be a great initiator. Skarner has four AP ratios, including 80% on his W's shield, and 100% on his ult. With enough AP and MS, he even becomes a tanky assassin, which is pretty amazing. He lacks the burst damage of similar tanky AP junglers such as Maokai, but he insane DPS, especially for a tank, and he has two powerful forms of CC. Due to his versatility, he fits into most team comps. The bottom line is that he's fun and totally viable, strong, in fact, at least in 3s. Plus, he's finally rocking an awesome skin: Guardian of the Sands Skarner .