Bath salts, the nickname for a relatively new type of designer drug that's been cited as the cause for recent violent attacks -- not to be confused with actual salts you put in your bath -- does cause hallucinations for some people, along with a laundry list of other psychological effects.
Methylenedioxypyrovalerone (MDPV), loosely agreed upon as the active ingredient in many bath salts, is under an emergency DEA federal ban, along with other, similar drugs in the cathinone family. It works like a stimulant, increasing activity in the nervous system in the same way as cocaine or Ritalin.
The reuptake of neurotransmitters norepinephrine and dopamine is inhibited, and if that's done with potent enough doses, it could lead to extreme paranoia and delusions. If a user's reaction is especially bad, they could end up doing something horrific in a drug-induced psychosis--such as eating someone, as in the now-famous Miami "zombie" attack."