"I don't think..."
I saw someone type in a chat "my messages aren't working, it doesn't seem"... and I hear people say, "It isn't working, I don't think" and things similar. I hear myself say "I don't think..." too often.
Now, really. When I'm saying something like that, I'm saying what I DO think, not what I DON'T think. It would be more accurate, instead of saying, "He's not there, I don't think," to say, "I think he isn't there." Because I DO think he ISN'T there... y'know? In the first example, it would have been more accurate for him to say, "It seems my messages aren't working." It DID seem that way... not it didn't!
Thus ends my grammar pet-peeve for the day.