You can never assume that other people, even the ones closest to you are like you. We all have our own brains and our own belief systems. With that said, I can't stand being told to "Have a blessed day".

With all due respect, when you say "have a blessed day" you are basically trying to put some of your Christian magic on me.  What if I don't want it?  What if my beliefs don't exactly measure up with yours? What if for some reason, I don't want to be "blessed".  You wouldn't like it (and I wouldn't last long) if I worked at a retail outlet if I checked you out and then I said "I CURSE YOU!". Now some people don't mean to "bless me" in any form, they're just mindlessly letting words spill from their brain while they wait for the next customer, that's kind of worse. Why say anything if you don't mean it?

This also applies to saying "bless you" after sneezing.  The other night I sneezed and my wife said "bless you" (she doesn't share my views on these kind of things) and I said, "uh, yeah, we need to come up with something better than that".  She then came up with the most random thing ever, she said, "what do you want me to say....a duck and a noodle?"  Now I have no idea what caused her to come up with that particular combination of words, but that's our new thing.  It's out with "bless you" and in with "a duck and a noodle".  My thought is if you're just going to let random words fall out of your mouth hole when someone sneezes or leaves, it might as well be "a duck and a noodle".