So my first thoughts when reading the topic were more among the lines of Louis furhter up. So despite what has been written before I share them with you anyway.

Three things that still get me:

1) gift, which means a present in English is spelled and pronounced exactly like the German word for poison. There's just so many possibilities for confusion there if you are not careful.

2) cell phones or mobile phones are called Handy in German. Handy is pronounced English as well and looks like a English word too if you dismiss the upper case. So a lot of people, even my profs at University have difficulty getting to grips with the fact that no English speaker will understand that a Handy is a cell phone.

3) eventually. That one is tricky for Germans as well. We have the word eventuell in German which means that something might or might not happen. While eventually means that it will definetly (yeah, yeah, I don't know how to write that word) happen. So a lot of people mix that up as well.