I have not really a catch phrase at all. I have said stupid things in the past, but still...

For example (In grade like 9...)

"You twat! Yes, that is right! I said TWAT!" I manage to say this in the most feminine way possible for me at the time. How embaressing...my friends still tease me about it.

*thinks*

"Knock yourself out" Is about all I can think of at the moment, but that is not unique to me