It's the only day when I don't have to do anything! I can sleep in or goof off all day and stay up as late as I want.
Sunday I have to prepare for school the next day so I can't stay up until sunrise.
Mon - Fri are school days so I'm always stressed on those days.
I can sit here and say I honestly do not know what day is my favorite. It just depends on the week and the day as to why it might be my favorite. I like a certain day each week, just depends on which each week =)