  We obtain a large class of new 4d Argyres-Douglas theories by classifying
irregular punctures for the 6d (2,0) superconformal theory of ADE type on a
sphere. Along the way, we identify the connection between the Hitchin system
and three-fold singularity descriptions of the same Argyres-Douglas theory.
Other constructions such as taking degeneration limits of the irregular
puncture, adding an extra regular puncture, and introducing outer-automorphism
twists are also discussed. Later we investigate various features of these
theories including their Coulomb branch spectrum and central charges.
