Aluminium is a big example in that it is readily reusable. Examples are milk container tops, medicine bubble dispensers, commodity bags, prepared sauces packs and chocolate inner wrap (some foreign chocolate has 100% foil wrap within card - a good design).

Avoidance is obviously the best solution. Otherwise, plastic inner wraps can be stripped off the aluminium, some easier than others. Outer wraps can also be removed with difficulty.

 

Paper is another type usually in labelling. Tearing off the plastic is possible but difficult. If the separation is incomplete put into soapy water and the paper will clump with bits of plastic in the lump but easily removable.