What are examples of over-the-counter stimulants?

Many kinds. Stimulants are drugs that activate physiological processes by acting on neurotransmitters. Caffeine based products liked Vivarin (caffeine) are an example. Decongestants containing pseudoephedrine & phenylephrine also have stimulant effects. All stimulants are dangerous when taken to excess & should only be used as directed. Consult your primary care doctor if you feel you feel chronically tired or drowsy.