I just came across this video
https://www.youtube.com/watch?v=GyJ6VpFqDYI of an internet blitz game where a GM whipped out this insane sequence as Black :
1. d4 Nf6 ; 2. c4 a6 (As I recall the standard idea is to use this defence as a transpositional tool to reach, depending on White's next move, either the Zaitsev variation of the Benko or a Modern Benoni with ...a6 and a4 included)
3. Nc3 but here instead of the usual 3. ...c5, Black came up with
3. ...b5 ; 4. cb ab ; 5. Nxb5 e5 !?!? ; 6. de Ne4 when White failed to respond adequately :
7. Qd4 ? Bb7 ; 8. e3 Na6 ; 9. Bd2 Bc5 ; 10. Qc4 and Black played the seemingly inaccurate
10. ...Qh4The rest of the game is worth watching if only for White's uncontrollable laughter at getting mated in picturesque fashion after the time-scramble.
Surely Black's opening cannot be remotely sound from a theoretical perspective, but it is looks like it could be a very fun blitz/surprise weapon. It is certainly born of some interesting ideas. The main one being that the standard Fajarowicz counter is not available here : 7. a3 ? Bb4+
What do you think is white's best here ? 7. Nc3 and 7. Nf3 Bb4+ ; 8 Nd2 spring to mind. Or perhaps refraining from taking the second pawn with something like 6. e3 is simplest.
Chess is such a wonderfully rich game. When you think you've seen it all, you continue to stumble acroos novel ideas on move 2 or 3 !