User blog comment:Roranoa zoro/Best Devil Fruit Combination/@comment-10302881-20130621043023

Yami Yami no Mi  [Marshal D. Teach] + Doku Doku no Mi  [Magellan]

Reason: Pull people into, your poision.

  Mato Mato no Mi [Vander Decken IX] +   Doku Doku no Mi  [Magellan]

Reason: Posion can be "directed" at your opponent.

Suna Suna no Mi [Crocodile] + Hana Hana no Mi [Robin]

Reason: Spawn hand on opponent, dry them out.

Hana Hana no Mi [Robin] +   Doku Doku no Mi  [Magellan]

Reason: Spawn hand on opponent, posion them.

Just so I won't have to keep repeating:

any logia that becomes a dangerous element with the Hana Hana no Mi [Robin]. So they can spawn dangerous elemental hands on the enemy.

Any paramecia that fire projectiles with the  Mato Mato no Mi [Vander Decken IX]. So they can fire their projectile at the enemy and never miss.