After really comprehending that I'm the actual last human on earth, I'd look for a really big house to live in, then I'd start to put a lot of food which expires quickly, in freezers. After that, I'd gather other types of food which can last multiple years. I don't have to worry much about the watertap not working because I live near a river. The problem will be the electricity, since it will eventually stop working because no one will be looking after it, togehter with that, the freezers will stop working. So I'd probably try to gather a lot of diesel generators but eventually, I'll run out of electricity. Well, so much for the things I need to survive. Now on to the other things.
To make sure not to go insane, I'd probably play games, watch movies and read books. Of course I'd just steal everything, if you can still call it that. This would mean that I have fianlly enough time to catch up on all the things I've wanted to read, watch and play for a while now but never found the time to do. I gues I'd also try to write a book, oh and educate myself on all kinds of different subjects.
At some point, I'd just take off my clothes and run around naked in my town, while laughing maniacally.