Also very common: "I am sat here". No you are not, you are sitting. Just stop it.
Also on here, I posted something and another poster quoted me, and changed the punctuation I had used. And they. were. WRONG. I was brave and said nothing (well, I said plenty) but it really did rile me.
There's a notice in our school library about pupils loaning the books. I have restrained myself, though with internal screams, from pointing out that it's the library that does the lending, not the pupils...