I think I'll steal a Xbox 360 or a Playstation 3 or a Wii, some games, a new desktop computer, a sword, a bass, a Nintendo 3DS, a flascard to 3DS, see if there's something new on Beasts of Midnight and steal the biggest television of a shop.
I would take a trip to several stores around the area and clear out the nicer TV's. Then take the large majority of Games/Movies/Music selections. Treat myself to large storage bins and move them into my house.
After I would raid bookstores for all Sci Fi/Fantasy books.
I would place hidden cameras in every store and stuff the day before you get your only person day, so I could sell all you guys out for legitley earned money.
Defiantly steal all the money I can get my hands on, drive my car non stop with no time wasted, go to nearest best buy, rack in all the electronic equipment I can fit into my car, than drive to apple store, take all iPhones MacBook etc and prob make a sandwich.
If I was the ONLY person on earth for a day, I'd do all the things I can't do when I'm NOT the only person on earth. That's a lot of stuff to do for one day.