Ok, so i love AP Corki. And it got very popular mid season 3. BUT there has been some corki changes/item changes that also make him a viable Marksman. I still think ap corki is amazing, as they made his q a larger range for maximum poke ( and in a hard lane farming is a breeze with his q". I still think its viable, he has amazing burst and some nice safe poke.

Ap corki may look like a troll build, but it's no joke. Ap Corki has an amazing burst, he scales well mid to late game, and his team fights are amazing because all his abilities are AOE. His passive helps with last-hitting, and helps lichbane do extra damage.

Pros/Cons

Pros

-Escape move Valkyrie
-Basic attacks are good for poking down enemies due to passive Hextech Shrapnel Shells
Awesome skins!
-Has nice poke and has good ratios
-Easily fills the tear of Goddess due to spamming R.
-All his damage is aoe, so he is amazing in teamfights.
-His passive gives lichbane 10% bonus damage, which actually helps a lot.
-Great Farmer!


Cons

-People will think your trolling
-you can fall off late game if you didn't farm/get kills
-If you run out of missiles in a fight, your basically screwed
-Early game to mid game he could get put off if he didnt get kills. Because that means he cant rush his lichbane/rabadons/archangels

well, lets see. He has an escape move to escape from ganks, which is really good on an ap mid laner. AD corki is behind for a LONG time because he has to rush his trinity, but with AP corki, the minute he hits level 6, he DOMINATES!

Begin game with corki is quite easy. start with two faerie charms and three health pots, you will have to sell one faerie charm later, but its good for begin game harassing. Basically as ap corki, you farm until level 6, and when you can land your q poke the enemy a bit. sometimes you get in some fights begin game, so that's why i grab Gatling gun at level 3. it helps deal damage and lowers there armor for corki's basic attacks to hit harder. But once you hit level 6, ap corki really starts to shine. his simple poke with his missles, and his passive procs bonus damage with the sheen, which helps tremendously in fights. Also, never under-estimate corkis w. It may only look like an escape for catching up skill, but the damage on it is absolutely AMAZING if placed under an enemy.

Mid game with corki is where he begins to do amazing burst. By now you should have rabadons and a lichbane. with the little team fights going on, his AOE missles and q does TONS of damage, and if you can position your w on all of them, that's a sure pentakill! Also, make sure you don't spam all your missles and miss them, because in a team fight with no missles can be deadly.

This is a standart ability sequence for ap corki, except for getting your Gatling Gun at level 3. I get gatling gun early to help me in small skirmishes early on. It reduces armor, and does decent damage. It also helps proc a sheen/lichbane.
These runes are very important. Because they have no magic resist+mana regen. But, it helps tremendously in game. Just think, corki shines at level 6 correct? so that means at level 6 he will have extra ap, for level 6, and late game.

With ap corki, i personally like the standard Flash and Ignite. But, im gonna tell you viable spells for ap corki, and some not so viable spells.

Viable with ap corki:

Flash Good escape move, even though corki has his W, it helps positioning also.
Ignite secures kills early game, secures kills late game. all around good spell.
Clarity Ok spell, i personally dont use it. But ap corki does use a lot of mana. So it isn't bad with him
Cleanse Cleanse is perfect with ap corki :D it helps remove the cc that midlaners usually throw. it's a great counter to many mid laners and it very helpful early and late game.
Barrier Another good spell with ap corki. protects you from some burst from the ap mid laner, and could save your life.
Teleport Overall good spell, you can recall when you want and barely miss your farm. also good for late game if theres a minion wave at your tower. so all around another good spell.


And now the Not so viable spells:

Exhaust If your randomly versing an ad carry mid, go head and take it. but if not, i wouldn't suggest it.
Heal Heal is better playing as ad corki, if you want a heal type move, i suggest barrier. it may not heal you, but it shields you from damage.
Smite Although, i would love to see a corki jungle, but your not corki jungle. So dont take smite.
Revive Oh come on. Must i explain?
Clairvoyance Leave this spell to the supports.

im gonna show you some hard opponents in lane with ap Corki. from a rate to 1 to 10 One being the easiest and 10 beings the hardest.

4/10 Just know to dodge her charm and orbs and you will be fine.
3/10 Just dont get caught be spears, and when she is level 6 you win trades with her.
7/10 Very hard lane, just play safe and ask your jungler to gank. but when you hit level 6 DON'T STOP POKING!
5/10 Somewhat easy, just save you W to get out of her ult and keep poking her. making her waste her shunpo is a good thing.
6/10 Be careful, if you get caught in his stun he will wreck you. just keep on poking, and play safe. Also when you see him miss his skills, take the opportunity to poke him with your q and basic attacks.
5/10 Some what easy lane, just keep moving, dodge the snare, and dont recall in obvious places when your low.
9/10 VERY hard lane. only the true ap corki masters could handle this lane, just make sure your always moving and when she gets her ult dont face her, try to make her waste it by W'ing out. and try not to get cought with he poisions, but other then that, POKE HER!
8/10 That stun can be very deadly, can quickly burst you. not only that, she builds tanky begin game so its hard to burst her. i advise MR and maybe some health.
10/10 MEGA hard lane. his lock on Snare counters you so hard, and once he hits level 6, his burst is higher then yours. i suggest not going corki if against a ryze. but if anything, play EXTREMELY safe and farm.
5/10 A ***** to verse because of stuns and slows, and her egg. but if you can w our of her ult, and not get hit by the stun, its an easy lane.
5/10 a pure skill matchup. You both arent so good before level 6, but the main thing with kassadin is, after he silences you, make sure you basic attack! He will end up lower then you are, and if you pop a q after the silence, you will Easily win that lane!

Ap corki is very good overall, good in teamfights, and by level 6 his burst is great. Either way he is a great pick mid lane. And don't downvote this guide until you try ap corki. Thanks for reading :D

PS First Guide :D