I have played 1.Nc3 for quite some time now.
...c5, 2. d4!? ...cxd, 3. Qxd4 ...Nc6, Qh4!? leads to even and highly unique games with many tactical possibilities on both sides if innacurate play.
...d5, 2. e4!? ...dxe, 3. Nxe is fairly self explanatory and easier to understand than:
...d5, 2. e4!? ...d4, 3. Nce2 (Nb1! has been played before as well with the idea that black's pawn is no better on d4 than d7 The game where B. Spasky was black ended in a rather quick draw) A few ideas behind Nce2 below~
3...c4, 4. white can play~ f4, Ng3, Nf3, d3...
3...e4, 4. white can play~ a3 (a must before d3 because you want to keep your dark squared bishop), Ng3, I have not tried it, but I have seen white play e5 with f4 to follow for a rather interesting struggle on both sides (but I cannot comment on how sound it is as of yet).
P.S. ~ I ignored the other main variations seeing as they have already been covered.
P.S.S. ~ A Correspondance GM (Ove Ekebjaerg) recently won 6/7 games as white in the CC World Championships using 1.Nc3! That is a winning percentage of 85.71%!!! The game he did not win ended in a draw. This score ensured him AT LEAST second place in the tournament!! His competition was 100% other GM's.