I think an underrated pokemon in this tier is Clamperl, which, with the modest nature and the deepseatooth, runs 608 SpA... Played in a trick room team, obviously.
Of course, the timid one (554 SpA) with shell smash is excellent too... Try to place it with a memento... Whimsicott is really good for that stuff. Dugtrio too, as it traps the opponent, places rocks, survives with the sash, and then, memento.
While the Clamperl's counters are down when you place it, your opponent is dead.
These are :
-magic guard sash (alakazam)
-powerful priority moves (extreme speed, some mach punches, sucker punch, talonflame...)
-focus sashes in general, but, you must have placed rocks when you play Clamperl.
-Shedinja, but the rocks kill it...
-great special walls which do not take super effective damages (chansey, blissey, grumpig...)
-things faster than +2 Clamperl (greninja, thundurus-I...) I usually try to place a sticky web, as defiants are not so common in this meta...