With the recent patch balancing out the AD + AP of Kat's ult, she has become as good as ever as a hybrid champion. With this build it's common to finish a game with 4 or less deaths, and if you don't have at least 20 combined kills/assists, you're not playing her right.

Pros

• lots of damage extremely quickly
• excellent ganker
• fun to play
• good chaser
• good escaper
• great for soloing
• excellent team-player
  
  Cons
• hard to master
• ult cancelled with stuns
• squishy

For you summoner spells, I find the most useful combination to be exhaust and ignite.

exhaust

• a must
• keeps enemy champ in range of ult
• reduced magic resistance with mastery

ignite

• can allow an early kill/first blood
• counters trynds ult
• finishes off fleeing champs

ghost

• probably the only other viable option
• can help with ganks
• can help escape (so does exhaust and shunpo)

Early

1. solo top
2. bouncing blade to harass enemy
3. killer instinct > bouncing blade if champ has healing abilities/deal full damage to all minions
4. if they push to much don't be afraid to used exhaust and ignite to get the kill
5. once you have sword of occult/hextech revolver/ult gank bottom if they have low enough hp

Team Fights

1. never initiate the team battles
2. focus their carry
3. killer instinct > shunpo > exhaust > ult > bouncing blade

Coming Soon...