Pros -
Massive damage output
Double jump/flash (great escape mechanisms)
Can carry entire teams if built properly
Large amounts of true damage through passive (very underrated)

Cons-
Squishy
Mana Hungry
Expensive build

Well, this is my first guide, and my build focuses on building large amounts of crit and AD. Most Corkis I see don't seem to utilize crit. I believe crit is invaluable on Corki as I hope to show in this guide.

For my runes I choose to get crit chance marks, Mana regen per level seals, flat health glyphs, and crit damage quints.

The marks give me a fairly good amount of crit for my build, since I find it somewhat difficult to crit early game and such, so it helps progress with crits early game, and helps late game as you have around 80% crit chance.

The mana regen seals are fairly important; Corki is a mana hungry champion. Although you are still mana hungry late game/early game, these runes help with overall longevity.

The health glyphs are helpful as Corki is a very squishy champion. They help provide him with a bit of that survivability that he truly needs.

For masteries I choose to go 19/3/8 route. This allows me to focus on crit + crit damage in offense, magic resist in defense, and regen/xp gain in utility. I get magic resist instead of the armor in the defensive tree because you gain armor every level. Points are put in regen from the utility tree in order to help Corki with his mana problems (especially early game). The offensive tree should explain itself.

Most people ask why O get two Infinity Edge's instead of a phantom dancer and an Infinity edge. This simple answer to this is the attack damage. Two infinity edges provide a sufficient amount of crit as well as large amounts of damage, making Corki very potent.

A few substitutes for items (aka the second Infinity edge or bloodthirster) could be

Hexdrinker - Perfect for a teemo/karthus, or anybody like that
Phantom Dancer - If you prefer the attack speed and crit
Banshee's Veil - If you need the survivability and mana
Frozen mallet - Health + slow
Last Whisper - Replace the Black Cleaver if the enemy team is that armor heavy.

Farming is EXTREMELY important for this build. I always take mid, and focus mainly on last hitting minions. If you do take mid (like you should) always remember to use Phosphorus bomb on champions AND minions (if you can). Harass with Missle Barrage by hitting minions and letting the AoE hit the enemy champions.

Focus on farming, harassing properly, conserving mana, and utilize crit as well as high amounts of AD.

This is my first guide and I hope you enjoy playing this Corki build as much as I do!