I've gotta add my contributions to this list too.
W. If you say 'bean burrito' three times, I'll ring up three bean burritos. Please be mindful of your stutter. Also please don't give your order backwards, by telling me all the alterations you want before telling me the actual item. (ie. "i need no tomatoes and no sauce on 3 tacos and 4 bean burritos and 2 tacos are no lettuce" ...etc). If you say "gimme six 5-layer burritos, two with no sour cream," I do not know if you mean eight burritos or six... I am forced to force YOU to clarify by asking, "Do you mean you want two 5-ayer burritos with no sour cream and then six 5-layer burritos regular?" And then you huff like I'm the idiot.
X. I know this has been said before but, Drive-thru custys... PLEASE... be involved in your order. I'm not psychic. If you don't know what you mean, I certainly don't either. If you don't AT LEAST look at the money in your hand as you hand it to me (let alone look at me as well), I am not reaching for it. I will assume you don't want sauce if you don't want to answer me after I ask 3 times. Don't act all offended because I didn't psychically know what you wanted.
Also, on the shrieking/screaming thing, oh GOD I HATE THAT. Please. Please for the love of god realize you are in front of a microphone that is connected to the ENTIRE KITCHEN'S EARS.
The same goes for diesel engine trucks! WTF do you need a vehicle like that for getting fast food anyway?!?!
Offtopic rant - I once had a woman phone me up to complain of a missing item and when I offered her a free meal as a replacement, she boasts of driving some large SUV and that I should replace the gasoline for having to return as well.
I was so blown away by the logic and couldn't help but respond, "Ma'am I'm not responsible for your choice in vehicles."
She cussed me some more and I repeated my offer and she hung up... luckily no corporate complaint about it...