A study from the International Journal of Medicinal Mushrooms reports that Dictyophora, a mushroom that grows on lava flows, induces spontaneous orgasms in about 1/3 of the woman who sniff it.

From Wikipedia:

According to a 2001 publication in the International Journal of Medicinal Mushrooms, the smell of the fresh fungus can trigger spontaneous orgasms in human females. In the trial involving 16 women, 6 had orgasms while smelling the fruit body, and the other ten, who received smaller doses, experienced physiological changes such as increased heart rate. All of the 20 men tested considered the smell disgusting. According to the authors, the results suggest that the hormone-like compounds present in the volatile portion of the gleba may have some similarity to human neurotransmitters released in females during sexual activity. The study used the species found in Hawaii, not the edible variety cultivated in China.