My pet peeves are the 2 more simple ones (and I'm sure they've been covered in other threads):

"your" for "you are" ("you're)
"there" for "their" (or even for "they're," i.e., "they are")

The ones that make me have to hesitate and think about the spelling are words like desperate, environment, occasion, and portrayal.

"Vaya con Dios, Castle. Go with God."
"God's going to sit this one out." The Punisher (2004)