  We study various conjectural dual descriptions of a stack of M2-branes in
M-theory including ADHM, ABJ(M), BLG, discrete gauge theories and quiver
Chern-Simons (CS) theories and propose several new dualities of the M2-brane
SCFTs by analyzing flavored supersymmetric indices in detail. The mapping of
local operators, Coulomb, Higgs and mixed branch operators as well as global
symmetries under the dualities are obtained from the precise matching of the
indices. Furthermore, we find closed form expressions for the Coulomb limit of
the indices of the $U(N)$ ADHM theory and the dual quiver CS theory for
arbitrary $N$ and propose a refined generating function for plane partitions
with trace $N$. For the quiver CS theories we also find an infinite-sum
expression for the Higgs limit of the indices which is more useful than the
original expression.
