Gourgeist-Super
Type: Ghost / Grass
Base Stats: 85 HP / 100 Atk / 122 Def / 58 SpA / 75 SpD / 54 Spe
Ability: Pickup / Frisk / Insomnia
Gourgeist-Super is a Pokémon whose defensive presence is most certainly threatening indeed. Once it has burned its foe with Will-o-Wisp, they are going to be hard-pressed to do much damage at all from the physical side. To put things into perspective, Gourgeist-Super is capable of taking physical attacks from powerhouses such as Mega Garchomp and then proceed to burn them, significantly decreasing their damage output. Gourgeist-Super also has access to the ever-annoying Leech Seed, which, coupled with Leftovers, gives Gourgeist a reasonable amount of recovery each turn, and a way to slowly wear down its foes. In addition, Gourgeist-Super has Shadow Sneak, which is a priority STAB move that can pick off weakened foes. Ability-wise, Gourgeist-Super benefits from the utility of Frisk - Being able to scout out the foe's item is a boon on such a bulky Pokémon, as by learning the foe's item, the user of Gourgeist-Super is often going to be able to have a clearer insight as to what set their opponent is running. Gourgeist-Super's Ghost/Grass typing also benefits it in a number of ways - It is immune to Normal and Fighting moves, Leech Seed, bothersome powder moves and has some useful resistances to boot. This Pokémon can easily halt physical attackers in their tracks given the chance, so make sure you have ways of dealing with it, or disposing of this Pokémon is going to be nothing but an uphill battle.
Jirachi
Type: Steel / Psychic
Base Stats: 100 HP / 100 Atk / 100 Def / 100 SpA / 100 Spe
Ability: Serene Grace
Jirachi is a very interesting Pokémon, to say the least. With a useful defensive typing, good, well-rounded stats and a large movepool, it is only natural that Jirachi can pose a defensive threat. Using its nice base 100 HP stat, Jirachi is capable of using Wish then passing the Wish to an ally with U-turn. U-turn also serves as a way of scouting and keeping up momentum. Jirachi is also able to set up entry hazards in the form of Stealth Rock, and with Jirachi's combination of defensive typing, speed and bulk, it is usually going to get the chance to set them up. Beyond Wish, U-turn and Stealth Rock, Jirachi can use its flinch-inducing utility to its advantage, with Thunder Wave and Body Slam for paralysis, and Iron Head for a reliable STAB that will often prevent its paralyzed foes from moving, allowing Jirachi to garner Leftovers recovery and wear down its foe. Jirachi always has many tricks up its sleeves, so should not be taken lightly.
EDIT: See Jukain's post - I have re-written Gourgeist-Super's article as a defensive one, like it should have been.