My favorites are:
~Tiny Woods (it's just so CHALLENGING). I almost always die with all those wurmples, exegcuttes, pidgeys and sunkerns. And that huge monster house on floor 3, worst than the one in 75F of silver trench, was terrible. Let me tell you waht happened:
Articuno was at f3 and it was terrible, from one side,wurmples were string shooting, exegcutes were hypnotizing (verb of hypnosis , lol) pidgeys were sand attacking and sunkerns were absorbing and from the other side, even more pokemon were arriving and started to kill my articuno. After 10 seconds powder snow didn't have pp so there was nothing to do. Just wait, wait for someone to rescue it. Wait for an absolution.... Since that day, the bosses took power of tiny woods (Exeggcutor, Pidgeot, Sunflora and Beautifly have been controling TW. No one has ever entered there again and articuno was never seen again....
~ Sky Tower: Everything's so cute (clouds are cute) (except for rayquaza, horrible) and has my favorite dragon poke, SALAMANCE.
~ Lapis Cave and Waterfall Dungeon: They're blue and I love blue. My serebii forums style is water-type. Also, I feel like in a diamond dungeon when I'm in lapis cave.
*Tiny woods thing: Just Kidding.....