aka The Mexican Defense aka The Kevitz-Trajkovich Defense.

1.d4 Nf6 2.c4 Nc6   

My defense against 1.d4 is the major weak point in my opening repertoire.  I have played The Grunfeld and KID against it, but I do not particularly like either.  I think this one might be the next one I test out, and I was wondering if anyone has insight into it.  Is it solid? Is it mainly transpositional? if yes into what?   Why is it so rarely played, only 770 games in games explorer,  when it scores so well, 33% wins? 

Most fun to play is 3.Nc3 e5 4.d5 Ne7 5.e4 Ng6 mostly followed by Bc5 or Bb4.
Unfortunately after 3.Nf3 e6 you still need to know a couple of different defences:
4.Nc3 Bb4 5.Qc2 - Zürich variation of the Nimzo-Indian
4.g3 Catalan (d5) or Bogo-Indian (Bb4+)
4.a3 d6 5.Nc3 g6 6.e4 Bg7 Delayed King's Indian. 
So it still takes a lot of preparation to play this. A good Tango repertoire is offered by Palliser's Tango! book.

I do play it, and I also own Palliser's book. I can simplly tell you it's an amazing opening, and I've won a lot a games in few moves, because white can get crushed if he/she plays carelessly.

I like the definition Palliser makes about this Mexican defense (or Tango) in his introduction: "The tango is a turbo-charged King's Indian"