For an in-game playthrough, items hardly matter. Therefore, you can use really anything you want. You could try an Expert Belt to boost super effective moves, a Spell Tag to power up Aegislash's Shadow Claw, a Metal Coat for Iron Head, or really anything else. As long as it can be used for multiple battles (for instance, not a Focus Sash or Sitrus Berry), then it works.
Hope I helped!