Tontine

Life insurance as a contest. Like...betting on yourself to live forever. This form of "investment" (and we're using the term broadly) involves a group of people paying sums of money into a central kitty. Each investor receives annual dividend payments from central funds. As people die, their shares get re-distributed among the remaining living investors. Eventually, everyone dies off but the final person. They get everything that's left.

Basically, a tontine provides a creepy combination of an annuity, a life insurance policy, and grimly watching your friends die to further your own financial gain.