The phrasal verbs are a bit of pain. My favorite ones are the ones with "look" (look up, look into, look out, look forward to, look after, look for and I surely forgot a couple), and the ones with "put" (put on vs. put off, put down vs. put up (with), put out). I can't put up with people who tell me that English is easy and I use these against them liberally .

And the pronunciation is just awful. When reading/writing, I can at least use the monumental Webster dictionary on the shelf next to me. But when speaking, I can't. Nobody knows how many times I mess up something in speaking...