There are a lot of weird, WTF movesets in the tower that seem to catch me off-guard. I've started assuming that if my opponents *can* have an ice move or a flying move, they will. Odd/dangerous pokes I've encountered (the highest I've gotten is 54 battles):
Latias with Psychic, Dragon Claw (IIRC), and Draco Meteor
Crawdaunt with Quick Claw, Arial Ace and Guillotine (the bane of the mid-20s - it always catches my Heracross lead with AA).
Slaking with Giga Impact, Flamethrower, and Blizzard (Completely caught me off-guard - I should have been able to answer it, but my Hera was KO'ed and I wasn't expecting a Blizzard from Slaking).
I lost at 54 to a freakin' Raticate (I was up 2 pokemon to 1) after missing twice and having the Raticate critical hit 3 times in a row.
I'm using Heracross, Regice, and originally a Flygon, now a Gliscor. All EV-trained. Heracross has Choice Band, but I'll probably switch him over to Choice Scarf now that I have enough points to buy it (I bought all the "Power" items first).