Pros:
-INCREDIBLE damage
-Extreme movility and harass (+no mana!)
-Hard to lane against
-One of the best roaming champions (INSANE ganks)
-When killing and assisting, your cooldowns are refreshed
-Has a game-changing ult that does insane damage
-Incredible champion at escaping or chasing
-Very good at farming
-Using kat correctly gives a free Normal win, and very easy early ranked wins (ppl need to know how to counter her)
-Easiest champion to do a pentakill with
-So sexy <3
-Extremely fun to play
-Feed and gg

Cons
-U have to know when and where to ult
-Can be hard to master correctly
-Squishy (depending on what u build)
-Can be countered, and focused a lot

Katarina is a very versatile champion with high movility and insane burst damage. I main her since im lvl 1 so i can affirm, that if played correctly a fed kat can win a game for her own.
Regarding items, the notes include all you need to know on how to build her. Runes and Masteries are the standard for ap melee champs.
I have done 43 pentas till now (yes, i count them), and 26 are with Kat.
I started playing ranked in Season 3 a couple days ago, and of course i used Kat. She is op if u don't know how to counter her in lane and in roaming. ALWAYS REMEMBER: If u can't feed at mid (jungle camping, counter-pick, etc) feed at bot, camp it and u should do well (always remind your support to buy a pink ward)


Here is a Normal Game i did pretty good, and scored 3 pentas



Here is another game i did nice, the other team tried to troll haha and they almost won, almost..



THANKS VERY MUCH FOR WATCHING THIS GUIDE!!!
---Guide's updated every day---
PainkillerGT