If I ended up as the last human on earth I'd start out by trying to get into ALL of the places that I really didn't belong. Area51, the Pentagon, the White House, dig up all that dirt that security so carefully keeps you out of. I'd probably accidentally off myself attempting to mess with a nuclear warhead somewhere just because I thought it would be fun
Of course I'd do all of this in a McLaren or something similar, playing with all the toys that I couldn't afford when limited by normal societal restrictions. Go to a military base and play with a Howitzer, find and air field and see if I could fly a stealth, break the Spruce Goose out of it's museum and take it for a spin, tour the Playboy mansion, and generally make an ass out of myself in ways that I normally couldn't even fathom.