In January 2016, Klaas Steenhuis gave us a summary of Losing Chess openings knowledge as at that date. The present summary updates it to take account of Mark Watkins's discovery that 1 e3 wins for White.
Known winning first moves for White
1 e3. This was finally proved to be winning by Mark Watkins and his computer in October 2016. For details, including some notes on the analysis as it proceeded, see Mark's web site http://magma.maths.usyd.edu.au/~watkins/LOSING_CHESS/. In particular, he has written a draft report
http://magma.maths.usyd.edu.au/~watkins/LOSING_CHESS/LCsolved.pdf
and there is also currently a browsable version of the solution
http://magma.maths.usyd.edu.au/~watkins/LOSING_CHESS/browse.html
though he doesn't know how long he will be able to host this.
Known losing first moves for White
1 d4, 1 e4, and 1 d3. These have long been known to be losing moves. They are very easy to win against, even for average human players.
1 Nc3, 1 f4, 1 Nf3, and 1 h4. These have been known for sixteen years or so to be losing moves. They are solvable by skilled human players.
1 b4 and 1 h3. These are much more difficult. In 2002/2003, Ben Nye reported having proved them by computer to be losing moves, but the proof trees appear not to have been published. Proofs became public when Mark Watkins solved them on his computers in September 2014, and Klaas published a shorter proof for 1 b4 in January 2016.
1 f3 and 1 c3. These are of comparable difficulty to 1 b4 and 1 h3. Computer-generated proofs by Klaas Steenhuis showing them to be losing moves were published in December 2014.
1 a3. This is considerably more difficult. A computer-generated proof by Klaas Steenhuis showing it to be a losing move was published in October 2015.
Moves still unresolved
The best-play results after the remaining moves, 1 Na3, 1 a4, 1 b3, 1 c4, 1 g3, 1 g4, and 1 Nh3, remain unknown. It would therefore appear that the game remains playable, at least for the moment, if White is restricted to one of these moves.
At least none of this invalidates any of the endgames which are the game's particular delight.