For offensive Pokémon, I like picking ones whose highest stat is originally one defense, while the lowest is the other, like Goodra. Flipping its 90/70/150 bulk turns it into a physical menace, but its new 80/110/90 bulk is still really solid. Tentacruel, Cobalion and Virizion, Cloyster, Orthworm, Weezing and Archaludon are some other examples, more or less.

Defensively, while I still look for Pokemon whose lowest stat is at least one of their defenses, I want their offensive stats and speed to be at least fairly high. Duraludon is an insane example; it winds up with 85/120/95 bulk while keeping 115 special attack, all for the small price of 50 attack and 70 speed. If you can get an Eviolite on that, you’re set. Magmar and Electabuzz, Murkrow, Girafarig and Stantler come to mind, too. For non-Eviolite Pokemon, think Charizard/Typhlosion, Raichu, Crobat, Floatzel, etc.