Herwig
From Particle Wiki
Herwig is a general-purpose event generator. Key features include built-in next-to-leading-order hard process calculation for all Standard Model processes, with matching to both angular-ordered and dipole shower modules via both subtractive (MC@NLO-type) and multiplicative (Powheg-type) algorithms; QED radiation and spin correlations in the angular-ordered shower; a consistent treatment of perturbative uncertainties within the hard process and parton showering.
