Iboga

Tabernanthe iboga
The root bark of this African shrub contains a hallucinogen called ibogaine which acts as a powerful stimulant. The result is great endurance for... well, whatever you may want endless energy for. Some native tribes in Gabon use it ceremonially for lion hunts, dancing, and all-night sex.
Since high doses of iboga may cause convulsions, respiratory collapse, and paralysis, it is considered a Schedule One drug. That means it is illegal in the U.S.