Or if you like something more adventurous, put half into developing a time machine and then half into repeating bitcoin speculations, accumulate them on a secure usb drive with s password protection, forget password and then give teams of world renowned hackers limited tries to break it. I've read about the last part a couple of months ago. They bought the same drives and claim that they reverse engineered them on a hardware level to get the idea how their software protection works. Yet, there just two tries left and the guy is not fast to reach an agreement.