Whoah. I just read this article on the Brazilian wandering spider. Turns out that it will give you a massive boner before killing you. According to the wikipedia article:
P. nigriventer venom contains a potent neurotoxin, known as PhTx3, which acts as a broad-spectrum calcium channel blocker that inhibits glutamate release, calcium uptake and also glutamate uptake in neural synapses. At deadly concentrations, this neurotoxin causes loss of muscle control and breathing problems, resulting in paralysis and eventual asphyxiation. In addition, the venom causes intense pain and inflammation following an attack due to an excitatory effect the venom has on the serotonin 5-HT4 receptors of sensory nerves. This sensory nerve stimulation causes a release of neuropeptides such as substance P which triggers inflammation and pain.
Aside from causing intense pain, the venom of the spider can also cause priapism in humans. Erections resulting from the bite are uncomfortable, can last for many hours and can lead to impotence. A component of the venom (Tx2-6) is being studied for use in erectile dysfunction treatments.
The amount of P. nigriventer venom necessary to kill a 20 g mouse has been shown to be only 0.006 mg intravenously and 0.0134 mg subcutaneously as compared to 0.110 mg and 0.2 mg respectively for Latrodectus mactans (Black Widow). This ranks Phoneutria venom among the most deadly found in spiders.
Whoah. Nature is freaky.