LSD
LSD is the most common type of hallucinogen, and also the most known. Sometimes LSD is also referred to as acid. LSD effects include color perception, and loss of control. Because you do not know what is real or not real, decision making is incredibly impaired, and you are incredibly dangerous will on LSD.
MDMA
MDMA, otherwise known as ecstasy or molly, is another very common type of hallucinogen. MDMA is often in pill form, and generally used in the party scene. Your entire social behavior is altered, and you have no control over your actions. Sweating excessively, rapid abnormal breathing, and a rapid heart rate is one of many effects from MDMA.
PCP
PCP is a less common hallucinogen that is extremely dangerous. When using this drug, seizures can occur. Users become heavily depressed, and suicidal. When using this drug, the user spaces out, and completely loses track of the physical world and their body.