Rocade chechmaye is the rarset.
What's the rarest kind of checkmate?
The smothered mate, especially when delivered by a knight, is one of the rarest checkmates. It happens when a knight strikes the final blow after the opponent's king is ensnared by its pieces. The Philidor's Legacy pattern is a well-known illustration. The underpromotion checkmate, in which a pawn advances to a knight rather than a queen to deliver mate, is another uncommon checkmate.

Get Eight rooks and the rooks should be in a way which controls every single square on the chessboard except the squares blocked by the king but it cannot mve because is X-ray defended. This should be the rarest checkmate.

The smothered mate, especially when delivered by a knight, is one of the rarest checkmates. It happens when a knight strikes the final blow after the opponent's king is ensnared by its pieces. The Philidor's Legacy pattern is a well-known illustration. The underpromotion checkmate, in which a pawn advances to a knight rather than a queen to deliver mate, is another uncommon checkmate.
Yeah this is a rare checkmate but I have done it like 20 times not in a row but have done.
Bro this underpromoion mate is totally rare I have never done it except once against Martin bot.
in 42 years of playing chess I only see it in diagrams mate in 1