What functions better with dual action?

Question

I am trying to find examples of things which function better in pairs or with dual action. Example is a sponge with one rough side for scouring and the other for soft cleaning. Something along those lines where the two parts compliment each other.

Answer 1

Windscreen squeegie - rubber on one side (for water or condensate) and rigid on the other (for ice).

Bottle openers - cork screw and cap opener.

Aquarium cleaning magnets, scourer one side, soft sponge other so glass not marked.