I wouldn't call myself a grammar nazi, but there are several commonly misused words that drive me insane. It's funny because there are times when my grammar drives my wife crazy. I'm completely comfortable with my bad grammar though.

heres an example.
"Ekspecially" :especially
I don't think a day goes by that I don't here someone throwing an extra letter into the word especially. What's more, when I've corrected people, they look at me like I'm an idiot.

Another one that I here all the time.
"Foward" :forward
I even here educated people say it. I think this one bothers me so much because without the R your not moving toward the front( or "fore").

Here's one more.
"A scissors" :A pair of scissors
I can overlook a person saying "a scissor", but "a scissors" drives me nuts. I often hear people doing this with pliers too. It's plural because it's one thing that's comprised of two equal main parts. The same goes for glasses or shorts. Would you go shopping for a sunglasses?

I usually try to ignore it because it seems rude to correct strangers. But sometimes I think it may be ruder to let them go on speaking incorrectly.

My wife corrected me at a family function when I said "I ain't got no keys". I shrugged my shoulders.

Guess I ain't got no grammar neither!