  We review the recent progress in new lattice fermion formulations. We focus
on the following three types which have possibility of improving lattice
simulations. (1) Flavored-mass fermions are a generalization of Wilson fermions
with species-splitting mass terms. In particular, staggered-Wilson fermions
initiated by Adams have possibilities of reducing numerical costs in overlap
fermions and the influence of taste-breaking in staggered fermions. (2)
Central-branch Wilson fermions, in which additive mass renormalization is
forbidden by extra axial symmetry, could enable us to perform Wilson-fermion
lattice QCD without fine-tuning. (3) Minimally doubled fermions, which reduce
the number of species by species-dependent chemical potential terms, realizes a
ultra-local chiral fermion at the price of hypercubic symmetry. These setups
reveal unknown aspects of lattice fermions, and we obtain a deeper
understanding of lattice field theory.
