What is the safest anti-psychotic medication on the market?

Nothing is safe: No medication is safe if used with out medical supervision.

Depends: Depends on what it is used for. In patient with dementia, there are no drugs in this class considered safer then another. However, for other problems, these drugs can be very beneficial. Many of these drugs are chosen for the side effect profiles to minimize problems and often to augment other meds or manage other symproms(like a sedating antipsychotic for someone not sleeping well.