How do I deal with Orianna's harass?
 

Because holy hell is it insane early game.

avoid the ball.

thats the point

MR?

Dodge the ball. Make her waste her mana (high mana costs), and choose champs with alot of long-range poke.

I only play the top two most fun champs in the game.

click left and right
case closed

Ball moves slow, is not that easy to dodge it, also orianna will make a point on having her ball near your turret, just stay right in front of orianna or right by her side so that she can't hit you with her shield.

Rengar and Kha'Zix?

Make her waste her mana.

It's been my experience that if you force a trade any time she harasses you, she'll run out of mana before you run out of health pots at which point you can go balls deep and force her to go back to base or die.