My big three are "just ignore those thoughts," "sure we all feel like that," and for the sake of my friend, "why can't you just hurry up." I don't really have any other than that, as far as frequently said things.

I actually think it's okay to ask someone with OCD "why do you do that?" if it's asked with sensitivity and genuine interest, but I guess you put it on your list because it's often asked with exasperation.