Favorite Cave/Dungeon? (Pikmin 2 only)

My favorite cave/dungeon would be the Subterranean Complex and the Hole of Heroes. Subterranean Complex has my favorite boss, and it's a good place to farm Purple Pikmin and White Pikmin. Hole of Heroes had lots of bosses and required you to really think things through. Loved them.

Submerged Castle I also like, though it can be a jerk especially when I do no-death runs. :p
Yeah, I'll have to agree with you there, although for Subterranean Complex, it's just for farming Purples and Whites.

Hole of Heroes have plenty of bosses, but I hate the Pileated Snagret boss there.

Submerged Castle can be fun at times, but yeah, it's annoying, especially if getting all the treasures in one go.

One of my favorites is Glutton's Kitchen, I loved battling against the Breadbugs.