A handheld shaker with a reciprocating agitator, comprising a mixing vessel that operatively contains a guide rod that runs from one end of the vessel to an opposite end of the vessel. The mixing vessel is operatively connected to both such ends. The shaker also uses a hollow agitator frame that operatively reciprocates from the one end of the vessel to the opposite end, and thereby mixes fluid contained within the vessel. A reciprocating agitator is also disclosed.