Incredibly, pills marketed at FPS players looking to improve reaction times have been debunked as hokum, according to this. Despite the maker of FPSBrain claiming its products provides a "remarkable increase in perception and reaction capacities", MTV called in a dietitian who begged to differ:
"In addition to caffeine, most...[energy] drinks contain a high sugar content," said nutrition expert Danielle Marzano. "In combination these ingredients can cause a rush that will eventually come crashing down. Those sensitive to caffeine may even become dizzy and shaky. Taking this pill with an energy drink or taking more than the recommended dosage may cause these effects."
Turns out FPSBrain is just like an "energy drink" in solid form. Without as much caffeine. Sounds wicked.