sometimes it's stalemate if you go for a queen and winning if you choose a rook. As you said in some positions underpromoting to a knight may be with check and could win you a crucial tempo. I have never seen someone underpromote to a bishop.
Pawn Promotion
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Okay yeah, Tron, stalemate would make sense. That is a very good point.
Perhaps I am missing an obvious answer, but WHY would anyone want to promote their pawn to anything OTHER than a queen? I could possibly see a configuration in which a knight could be more beneficial if the positioning is such that an L shape could lead to a faster mate than queen movement, but a bishop or a rook to me is a ridiculous choice as the queen can do those things and more. Does someone have a good rationale as to why someone would select a rook or a bishop? I really am curious.