assuming using specific familiar abilities, and assuming no specific picks or combo?

I can't quite parse what you mean by that, do you mean with either or?

You could give it Masters Form and a shield to have it bodyblock, and Lifelink to keep it alive when it takes hits. This strategy is best used on a Champion or Monk, rather than a wizard or witch.

You can use it as a 1-day "Quicken Spell" with the Spellcasting ability.

You can load it up with Skilled (Specific Lore), Independant, and Speech abilities to act as a free-action enemy scanner.

A familiar can't quite activate an item, but it can release an item from a high distance using Manual Dexterity + Flier, breaking open jars containing items affected by Shrink Item, or Inhaled Poisons.