Things said way too often in the studio, I'll start.

Being in a band, the only thing that irritated me was when people name dropped and also, this

"I dont have a million dollar studio, but i can get you the million dollar sound"
 
*After pretending to change something on request.. this HAS happened many times..*

Band member (usually a guitarist.. funny that): "Oh dude that's MUCH better"
Me: "Yep.. I didn't actually change it *points* see? Now you don't get a say anymore :p"