The magnetic properties of icosahedral MRu12 clusters are studied using the discretevariational local-spin-density-functional method, where M=V, Cr, Mn, Fe, Co, and Ni. The results show that all of the Ih MRu12 clusters, just like the case for the Ih Ru13 cluster, have double magnetic solutions. In contrast to the moment of 4μB for the Ih Ru13 cluster, the total magnetic moments of the Ih MRu12 clusters, ranging from 1μB to 20μB, have been changed greatly by the substitution of the central Ru atom with M. Among them, the NiRu12 cluster has a giant moment of 20μB. Furthermore, the NiRu12 cluster has nondegenerate ground state and could be expected to be remarkably stable. Therefore, for the purpose of enhancing the magnetic moment of the Ih Ru13 cluster, Ni is a promising candidate as a dopant. Finally, we predict that all the Ih MRu12 clusters except NiRu12 might belong to the class in which the magnetization of the cluster increases with temperature.