Nearly all trumps that inflict damage are air unblockable/overheads (Selvaria's rifle, Taiga's trashcan). You can only block them with a standing guard, but you still get that huge pushback. On the upside trumps are vulnerable to throws, but it might not be worth the risk unless you know it's coming.
I gotta say i like Kirino's since you can set up unblockable combo's from her trump.