Ernest Hemingway, because if it were only for a day, then I could give death a try for a bit without the level of commitment that's usually required.
If I were to be a famous person, it would be Bette Midler. I love her bold and comedic personality, she oozes confidence. Bette has a rich velvety voice, well, to my ear anyway. She's been a very successful actress and singer, who has an ability to slap a little comedy around too! What a package.
"Which celebrities life would you ruin in one day?" Good question. If the thought of using some random famous schmucks ding a ling in the bathroom didn't make me feel... disgusted, I'd have a life to ruin.
Beren Erchamion, so that I could touch a Simaril with my hand. Wait, does this have to be a real person?
Character Moominpappa from Tove Jansons Moomin books. https://en.wikipedia.org/wiki/Tove_Jansson https://en.wikipedia.org/wiki/Moomins
Ooh if I could be a famous person for one day who would I be? Um, I am thinking. Probably a smart gal who can program just about anything. For past women Ada Lovelace. for current I am not sure right now. Maybe for present JK Rowling for authors or someone.
Garrus Vakarian (Mass Effect) Well, I guess as a character in anything. But famous person? Maybe Howard Hughes before he turned recluse.
You are welcome. Moomins are great reading in every age. If you don't know Fennoscandian children's books, here you have some tips: https://en.wikipedia.org/wiki/Astrid_Lindgren https://en.wikipedia.org/wiki/Tove_Jansson https://en.wikipedia.org/wiki/Hans_Christian_Andersen https://en.wikipedia.org/wiki/Mauri_Kunnas https://en.wikipedia.org/wiki/Gösta_Knutsson