  We study sequential tunneling through a metallic nanoparticle close to the
Stoner instability coupled to parallely magnetized electrodes. Increasing the
bias voltage successively opens transport channels associated with excitations
of the nanoparticle's total spin. For the current this leads just to a steplike
increase. The Fano factor, in contrast, shows oscillations between large
super-Poissonian and sub-Poissonian values as a function of bias voltage. We
explain the enhanced Fano factor in terms of generalized random-telegraph noise
and propose the shot noise as a convenient tool to probe the mesoscopic Stoner
instability.
