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 6.5 \times 10 ^ { -5 } photons cm ^ { -2 } s ^ { -1 } , about six times the flux of the brightest \gamma -ray steady source , the Vela Pulsar .