My biggest pet peeve has got to be saying "said," too much. For intance...
QUOTE
"Hi," said Bob.
"Hi," said Jake.
"How are you?" Bob said.
"I'm alright," said Jake.
:devil: There are plenty of other words besides "said,": replied, asked, commented...

But I guess that isn't really grammatic...

Here's one grammatic one: "it's" and "its." <_< Now THAT is annoying.