  I. Introduction   II. Two-dimensional lattice fermions   III. Methods to avoid fermion doubling (sine dispersion, sine plus cosine dispersion, staggered lattice dispersion, linear sawtooth dispersion, tangent dispersion)   IV. Topologically protected Dirac cone   V. Application: Klein tunneling (tangent fermions on a space-time lattice, wave packet propagation)   VI. Application: Strong antilocalization (transfer matrix of tangent fermions, topological insulator versus graphene)   VII. Application: Anomalous quantum Hall effect (gauge invariant tangent fermions, topologically protected zeroth Landau level)   VIII. Application: Majorana metal (Dirac versus Majorana fermions, phase diagram)   IX. Outlook 
Tangent fermions: Dirac or Majorana fermions on a lattice without   fermion doubling