Sorry, I used to play him alot and rush black cleaver for the added armor pen, though I misinterpreted my old build and was thinking it was automatically applied it. I forgot that it had to be manually applied, which is still very effective as you mentioned.

Eitherway, my old build revolved around high damage output with Black cleaver, Bloodthirster, Frozen Mallet (I think) and Infinity edge if possible. Depending on the game, this leaves you free to get 1 armor or survivability item of any kind, or two if you drop one of the items I listed (given they are all high cost items). Boots depend on the game, just remember to try to keep Valkyrie off CD for the escape, and attack speed is not necessary when you have his gatling gun. Late game you'd be a fool to stand in it.

I used to play solo mid carry AD Corki exclusively, but I've been trying out AP Corki lately. It's fun, but it doesn't feel quite as strong as AD Corki come late game. Because of Corki's bad AP ratios, I focus on magic penetration: Sorcerer's Shoes, Haunting Guise, Rylai's, Void Staff

Before I played corki I mostly played mages and was really fed up with stacking the same AP items all the time - but I wasn't familiar enough with AD to build an AD Corki.

My corki is a (to me, fun) mix of both. Since I start with sheen I'm required to spam spells during battle anyways so I might as well have some AP to boost that spell damage!

I build:

1. Amplifying tome + Health Pot (Crystal + 2 pots is smarter, but I'm an aggressive ass)
2. Sheen + whatever boots fit the situation

3. First decision: Rageblade or Rylai's
If you've managed to make a few burst kills with sheen, you can keep going down that lane by building a Rageblade. I try to get the Pickaxe first for extra last-hitting minion ease.

If you're forced to play cautiously, throwing rockets at the enemy from afar or simply forced to Valk out of battles early, go for Giant's Belt. Once you have Rylai's you can (assuming you're still playing defensively) slow any pursuers you have.

4. If you got the Rageblade, get Rylai's as 4th. If you got Rylai's get Rageblade as fourth! To me they're both essential items for Corki.

5. Is the game dragging on this far you can go for Trinity force, Stark's Fervor or Infinity Edge. No need to get Frozen Mallet because you're already slowing the f out of everyone!
(Wait, or does Frozen Mallet stack with Rylai's? That'd be AWESOME!)



This build works really well for me since it 'encourages' (forces) me to make full use of both sides of Corki, getting my hands dirty in teamfights as well as hunting down the stragglers.