Here's a short and silly list of some of the dumb things I've said in German:
In general conversation
What I meant to say: I'm impressed!
What I said: I'm impressive!
At work when speaking to customers
What I meant to say: Serve yourself!
What I said: Behave yourself!
What I meant to say: It's spicy.
What I said: It's bland. (Fortunately, that mistake was rectified before purchase.)
What I meant to say: One can sit at the window (gestures to window seating).
What I said: One can sit in the window (gestures to window seating). I then imagined those poor customers trapped in the glass like a bug in amber. Oopsie!
Any of you out there in ex-pat land have any verbal gaffs that you'd like to contribute?