I don't really notice when I use foreign words, normal English has so many of them. I know 'foreign' itself is French, but I wouldn't have considered 'angst' or 'pretzel' until I read Ingo's list, then I think 'oh, that does sound German' (for example). I noticed "Sturm und Drang" wasn't on there, I think quite a few non-German speakers are familiar with the phrase.
There's some other things I say more intentionally. (There was only a few, but I keep remembering more)
-Almost always use one of these instead of 'cheers'.
-I curse in other languages pretty frequently (Chiefly 'British', but that still counts, doesn't it?)
-I quote this thing sometimes, but that's not real German, is it?
-Mai ben lai: A Thai phrase, I'm told it roughly translates as 'it doesn't matter/don't worry about it'. I use it quite a lot.
-Hc Svnt Dracones: Latin, it's the earliest known use of the phrase "here be dragons". I use it to mean "I don't know about this and it doesn't matter, don't ask me."
-Felix Natalis Solis Invicti: Explained here. I put 'felix' on the front because it means 'lucky/happy', so it's supposed to be "happy birthday of the invincible sun", but it's probably not grammatically correct Latin. I say it to people who wish me merry Christmas, because I like being confusing.

There's some more, but not very often.