When I live I cry, if you don't kill me I'll die. What am I?

Why this works

This riddle plays on the dual meanings of "cry" and "die." When a candle is lit (or "lives"), it produces wax that melts and drips down, resembling tears, which is the "cry" part. The second part, "if you don't kill me I'll die," refers to the candle's flame being extinguished (or "killed")—if you don't blow it out or let it burn out completely, it will eventually consume all its wax and "die" as well. This clever use of life-like qualities for an inanimate object makes the riddle both engaging and thought-provoking!