With the students I had, their most over-used words where..
-Sorry Sir
-Okay Sir
Remarkably both words would be used repetitively during flight training, and the more times they made the same mistakes over and over again, the amount of "Sorry and Okay" were used....
But I do admit I used "maybe" quite a bit... generally answering students questions regarding if we can fly today or not... (although they would get a better answer form dispatch since dispatch never told flight instructors what was going on).