user11144: A regular game has been played where White still has all 16 pieces. White promoted only a single pawn, and not to queen. In the final position all 16 pieces of White have (at least) one mating move. Yes, also the king. Find the position. ("The"=it is mostly determined, allowing for variations)
Yes, fitting for Silvester there is a little gag hidden, but it is entirely conforming to FIDE rules.

user33803: This is a solution that comes with a promoted bishop. All 16 white pieces have at least one mating move, the star among them being 0-0-0#.
A problemists problem with this is, as was pointed out by OP, that it's an impossible position due to black's double pawns.
[fen "1nbBbb2/PP1P1PP1/1BpkBQ2/2p1p1N1/1P3P2/2N4R/8/R3K3 w Q - 0 1"]


11144: <p>A regular game has been played where White still has all 16 pieces. White promoted only a single pawn, and not to queen. In the final position all 16 pieces of White have (at least) one mating move. Yes, also the king. Find the position. (&quot;The&quot;=it is <em>mostly</em> determined, allowing for variations)</p>
<p>Yes, fitting for Silvester there is a little gag hidden, but it is entirely conforming to FIDE rules.</p>
 33803: <p>This is a solution that comes with a promoted bishop. All 16 white pieces have at least one mating move, the star among them being 0-0-0#.</p>
<p>A problemists problem with this is, as was pointed out by OP, that it's an <em>impossible position</em> due to black's double pawns.</p>
<pre><code>[fen &quot;1nbBbb2/PP1P1PP1/1BpkBQ2/2p1p1N1/1P3P2/2N4R/8/R3K3 w Q - 0 1&quot;]
</code></pre>
