The trident is a spiritual symbol that has significance in many religions, both modern and ancient.   Christians often think of it in relation to Satan, or devils in general.  Devils are often depicted carrying a trident.  This could be because early Christians, in an effort to separate themselves from pre-Christian religions, often started depicting holy symbols of other religions as tools of the devil.  
    The trident has three prongs coming from one handle so symbolizes many things that come in threes.  It can symbolizes the Father, Son and Holy Spirit of Christianity.  It can symbolize the three regions or time: past, present and future.  It can symbolize the three jewels of Buddha, the Dharma and Sangha in Buddhism.  It represents the three root poisons of the mind and spirituality: anger, sloth and desire.  It is the weapon of various ancient gods including Zeus, Poseidon and the Hindu god Shiva.  Poseidon caused earthquakes when he struck the ground with his trident and storms when he stirred it in the sea.  Zeus fired lightning bolts from his.  An early Christian symbol found in the catacombs of Rome depicts a trident between two fish.  The French fleur-de-lis is a variation of the trident.