not so rare as you think
What's the rarest kind of checkmate?
Around 1 min
You are the fastest!
Well did you copy paste or something else?
He sent a shorter one and he did copy paste
https://www.chess.com/game/live/136605001605
not so rare... I manage to make even more than one per day in some periods... but funny
Double disambiguated bishop capture checkmate
The explanation is in this YouTube video:
While a couple of those moves are rare, happening zero out of 342 billion times, it seems like they would be tied with the 30% of moves never seen. Also at zero.
It's hard to say how many of those 114 billion moves never seen are checkmate, but it's probably a lot. Which is to say that all of the rare checkmates that people have suggested so far are not the rarest. Because they have happened at least once.
The madman's mate:
g4 - e5
f3 - Qh4#