My pet hate is when I see 'brought' used... as in:-
"I brought an ice-cream from that van over there, but now it's melted"
I see it used on a lot of forums. It's not laziness, because it's got an extra letter... so I just don't get it.
I must admit to getting apostrophe wrong myself quite often. Plural, belonging to... leave it in, put it at the end.. arrggh.