お気に入り boss fight in any mario game?

So what is your お気に入り boss fight in any Mario game?(Excluding final bosses)

My お気に入り would have to be either the battle with giant bowser in Mario and Luigi dream team, The Bouldergeist from Super Mario Galaxy, Raphael the Raven from Yoshi's island and pretty much every boss from Paper Mario TTYD.

How about you?