Terrakion @ Coice Band/Choice Scarf
EVs: 4 HP / 252 Atk / 252 Spe
- Close Combt
- Stone Edge
- Sacred Sword/Earthquake/Quick Attack
Close Combat is nice STAB move, and STAB Stone Edge compliments it extremely well.
X-scissor hits Psychic types more reliable, and a bit harder than Stone Edge.
Sacred Sword is here if you don't want to lower Terrakion's defenses, Earthquake is pretty redundant with CC, but it hits some things harder, like Jirachi.
Quick Attack is priority and is an option for the Choice Band set.
As for natures, Adamant can be used on the Choice Banded set, but you won't outspeed as much which can be key sometimes. Nevertheless, Adamant does do more damage, and works well on slower opponents.
Adamant can also be used on the Choice Scarf set, for a powerful and fast attacker, while Jolly has more of a "revengekilling" role.
I just saw you want a tank, Terrakion can be paired with Tyranitar or Hippowdon to give it a nice 50% SpD boost, helping it take hits.
It also has respectable natural bulk, having 91 / 90 / 90 HP and defenses, respectively.