Since 2007, the blazar 3C 454.3 has become the most active and the brightest gamma-ray source of the sky, deserving the nickname of Crazy Diamond. The short-term variability in the gamma-ray energy band and the extremely high peak fluxes reached during intense flaring episodes make 3C 454.3 one of the best targets to investigate the blazar jet properties. We review almost four years of observational properties of this remarkable source, discussing both short- and long-term multi-wavelength campaigns, with particular emphasis on the recent flaring episode which occurred on 2010 November 20, when 3C 454.3 reached on a daily time-scale a gamma-ray flux (E>100 MeV) higher than 6.5E-5 ph/cm2/s, about six times the flux of the brightest gamma-ray steady source, the Vela Pulsar.
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