LSD is sometimes sold as glue which is placed on the back of stamp that can be licked off so that the user is able to experience the effects of the drug.
The common paranoia-inducing effects of cannabis can cause bad magic mushroom trips.
Some Ecstasy users experience negative effects right away and may become anxious and agitated.
PCP's effects can vary from person to person and dose to dose, mainly because of significant variations in amount and composition of active compounds.