Who's-Whose.
Poor, pore and pour
Its and it's
Pedal, Peddle, Petal, Paddle (often mis used in Fuchs threads and gas pedal threads) I roar at that one.
Or, should I say that one "sleighs" me?
Here's one form the 991 bbs today:
"this engine is a 80sc 3.0 liter with mettle lines."
(I won't identify the poster)