Pre workout is the big one. Some people actually grow to like that tingly feeling in your ears and face caused by beta-alanine lol. I train with some guys who I honestly think it's in their heads. If their jar runs out, they can't lift for shit. I think they spend too much time worrying that they don't have their powder instead of just fucking working.
Hell, I don't take much in the way of stim based products but I know people who drink so much of that crap they've become immune.