I consider Methyphenidate (semi-strong amphetamine) to be a poteint substance for a "high."
Can be mentally addictive, like all amphetamines, unless you moderately dose it. It stimulates the dopamine levels within your brain. Excess dopamine causes a hallucinogenic effect, I don't reccomend this, but a way to accelerate this is to snort substantial quantities, with short durations between intake. Another intake method; rest a 20 mg Ritalin under the right side of your tounge (dissolves into artery) and let it dissolve thoroughly. As it dissolves, you may "tweak". It strongly stimulates your dopamine this way, and may influence euphoria, sedation, or hallucinogenic effects. If I, in any way, have given incorrect information, within this comment, please alert me, and justify. Thank you.